Method for transmitting D2D discovery signal by terminal in wireless communication system and terminal using same method

ABSTRACT

A method for transmitting a sidelink discovery signal in a wireless communication system, the method is performed by a user equipment (UE) and includes: determining a transmit power for the sidelink discovery signal, and transmitting the sidelink discovery signal with the transmit power, wherein the transmit power is determined based on discMaxTxPower, and wherein the discMaxTxPower informs a parameter used to calculate a maximum transmit power of the UE configured with a concerned range class.

CROSS REFERENCE TO RELATED APPLICATIONS

This Application is a Continuation Application of U.S. patentapplication Ser. No. 15/546,536 filed on Jul. 26, 2017, which is theNational Phase of PCT International Application No. PCT/KR2016/000863,filed on Jan. 27, 2016, which claims priority under 35 U.S.C. 119(e) toU.S. Provisional Application No. 62/108,529, filed on Jan. 27, 2015,U.S. Provisional Application No. 62/109,635, filed on Jan. 30, 2015,U.S. Provisional Application No. 62/114,005, filed on Feb. 9, 2015, U.S.Provisional Application No. 62/165,952, filed on May 23, 2015, and U.S.Provisional Application No. 62/169,544, filed on Jun. 1, 2015, all ofwhich are hereby expressly incorporated by reference into the presentapplication.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to wireless communication, and moreparticularly, to a method of transmitting a device-to-device (D2D)discovery signal by a user equipment (UE) in a wireless communicationsystem, and the UE using the method.

Related Art

Standardization works of international mobile telecommunication(IMT)-advanced which is a next generation (i.e., post 3^(rd) generation)mobile communication system are carried out in the internationaltelecommunication union radio communication sector (ITU-R). TheIMT-advanced aims to support an Internet protocol (IP)-based multimediaservice with a data transfer rate of 1 Gbps in a stationary or slowlymoving state or 100 Mbps in a fast moving state.

3^(rd) generation partnership project (3GPP) is a system standardsatisfying requirements of the IMT-advanced, and prepares LTE-advancedwhich is an improved version of long term evolution (LTE) based onorthogonal frequency division multiple access (OFDMA)/singlecarrier-frequency division multiple access (SC-FDMA) transmission. TheLTE-advanced (LTE-A) is one of promising candidates for theIMT-advanced.

Meanwhile, recently, there is a growing increase in a device-to-device(D2D) technique for performing direct communication between devices. Inparticular, the D2D is drawing attention as a communication techniquefor a public safety network. Although a commercial communication networkis rapidly changing to LTE, the public safety network is primarily basedon a 2G technique at present in terms of costs and a problem of acollision with the conventional communication protocol. Such a technicalgap and a demand on an improved service results in an effort ofimproving the public safety network.

The public safety network has a higher service requirement (reliabilityand safety) in comparison with the commercial communication network, andin particular, even if cellular communication is performed in anout-of-coverage state or is not available, also demands direct signaltransmission/reception between devices, i.e., a D2D operation.

The D2D operation may have various advantages in a sense that it issignal transmission/reception between proximate devices. For example, aD2D user equipment (UE) may perform data communication with a hightransfer rate and a low delay. Further, the D2D operation may distributetraffic concentrated on a base station, and may have a role of extendingcoverage of the base station if the D2D UE plays a role of a relay.

Meanwhile, the D2D operation includes D2D discovery and D2Dcommunication. The D2D discovery is a procedure used when a proximityservice-enabled UE discovers another proximity service-enabled UE. TheD2D communication is a procedure for directly exchanging data betweenproximate UEs. Which method will be used to determine transmit power isa matter to be considered when transmitting a signal for the D2Ddiscovery.

Further, transmission of a synchronization signal and a broadcast signalis necessary for the D2D discovery and the D2D communication. Thesynchronization signal for the D2D communication is referred to as asidelink synchronization signal (SLSS or SSS) to distinguish from asynchronization signal used between a base station and a UE in theconventional wide area network (WAN). For the same reason, the broadcastchannel for the D2D communication is referred to as a physical sidelinkbroadcast channel (PSBCH).

The SLSS/PSBCH may be expressed as being triggered for the D2D discoverywhen it is transmitted for the D2D discovery, and may be expressed asbeing triggered for the D2D communication when it is transmitted for theD2D communication. When the SLSS/PSBCH is triggered simultaneously forboth of the D2D discovery and the D2D communication, how to determinetransmit power of the SLSS/PSCBH may be a matter to be considered.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method oftransmitting a device-to-device (D2D) discovery signal, performed by auser equipment (UE), in a wireless communication system, and the UEusing the method. In addition, there is provided a method oftransmitting a sidelink synchronization signal and a physical sidelinkbroadcast channel, and a UE using the method.

In one aspect, provided is a method of transmitting a device-to-device(D2D) discovery signal, performed by a user equipment (UE), in awireless communication system. The method includes receiving powerinformation discMaxTxPower for D2D discovery signal transmission anddetermining transmit power PPSDCH for the D2D discovery signaltransmission on the basis of the power information discMaxTxPower.

The D2D discovery signal may be transmitted with the transmit powerPPSDCH determined on the basis of the power information discMaxTxPower.

The power information discMaxTxPower may be received via a differentsystem information block other than a system information block forreceiving power information P-Max for D2D communication.

A range class may be configured to the UE, and the range class indicatesany one of short, medium and long.

The power information discMaxTxPower may indicate maximum transmit powerwhich must not be exceeded when the D2D discovery signal is transmittedaccording to the range class configured to the UE.

The transmit power P_(PSDCH) for the D2D discovery signal transmissionmay be determined on the basis of maximum output power P_(CMAX,c) at aserving cell c.

The maximum output power P_(CMAX,c) may be determined on the basis of apower value P_(EMAX,C) configured by a network and the power valueP_(EMAX,C) configured by the network may be determined by the powerinformation discMaxTxPower for the D2D discovery signal transmission.

In another aspect, provided is a method of transmitting a sidelinksynchronization signal (SLSS) and a physical sidelink broadcast channel(PSBCH), performed by a user equipment (UE), in a wireless communicationsystem. The method includes determining transmit power for the SLSS andthe PSBCH and transmitting the SLSS and the PSBCH with the determinedtransmit power. If transmission of the SLSS and the PSBCH is triggeredsimultaneously for both of device-to-device (D2D) discovery and D2Dcommunication, the transmit power for the SLSS and the PSBCH isdetermined on the basis of power information P-Max for the D2Dcommunication.

The transmit power for the SLSS and the PSBCH may be determined to adifferent value in case of being triggered for the D2D discovery and incase of being triggered for the D2D communication.

The power information P-Max for the D2D communication and powerinformation discMaxTxPower for the D2D discovery may be received viadifferent system information blocks (SIBs).

The transmit power for the SLSS and the PSBCH may be determined on thebasis of maximum output power P_(CMAX,c) at a serving cell c.

The maximum output power P_(CMAX,c) may be determined on the basis ofthe maximum power value P_(EMAX,C) configured by a network and the powervalue P_(EMAX,C) configured by the network may be determined by powerinformation P-Max for the D2D communication.

In still another aspect, provided is a user equipment. The userequipment includes a radio frequency (RF) unit for transmitting andreceiving a radio signal and a processor operatively coupled to the RFunit. The processor is configured for receiving power informationdiscMaxTxPower for device-to-device (D2D) discovery signal transmissionand determining transmit power P_(PSDCH) for the D2D discovery signaltransmission on the basis of the power information discMaxTxPower.

In still another aspect, provided is a user equipment. The userequipment includes a radio frequency (RF) unit for transmitting andreceiving a radio signal and a processor operatively coupled to the RFunit. wherein the processor is configured for determining transmit powerfor a sidelink synchronization signal (SLSS) and a physical sidelinkbroadcast channel (PSBCH) and transmitting the SLSS and the PSBCH withthe determined transmit power. If transmission of the SLSS and the PSBCHis triggered simultaneously for both of device-to-device (D2D) discoveryand D2D communication, the transmit power for the SLSS and the PSBCH isdetermined on the basis of power information P-Max for the D2Dcommunication.

According to the present invention, when transmitting a device-to-device(D2D) discovery signal, a user equipment (UE) can transmit the D2Ddiscovery signal on the basis of power information indicating a maximumtransmit power value which can be determined differently depending on arange class configured to the UE. Therefore, unnecessary wastes of powerand interference occurrence can be reduced. In addition, whentransmitting a synchronization signal and a broadcast channel for a D2Doperation, a transmit power value of the synchronization signal and thebroadcast channel may vary depending on for which D2D operation it istriggered, for example, whether it is triggered for D2D discovery ortriggered for D2D communication. If the synchronization signal and thebroadcast channel are triggered for both of the D2D discovery and theD2D communication, which one will be used to determine transmit power isambiguous, and this is clearly specified in the present invention.Therefore, ambiguity can be removed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a wireless communication system.

FIG. 2 is a block diagram showing the structure of a radio protocol onthe user plane.

FIG. 3 is a block diagram showing the structure of a radio protocol onthe control plane.

FIG. 4 shows a reference structure for a ProSe.

FIG. 5 shows examples of cell coverage deployment with UEs performing aD2D operation.

FIG. 6 is an exemplary embodiment of a D2D discovery procedure.

FIG. 7 shows another embodiment of a D2D discovery procedure.

FIG. 8 shows an example of a UE for providing relay functionality.

FIG. 9 exemplifies the aforementioned ‘CASE (1)’ and ‘Case (2)’.

FIG. 10 shows a discovery signal transmission method of a UE accordingto an embodiment of the present invention.

FIG. 11 shows a method of determining TX power for a D2D signal of a UEaccording to the aforementioned ‘Example #2-1’.

FIG. 12 shows an example of a method of determining TX power when anSSS/PSBCH is triggered for both of D2D discovery and D2D communication(or simultaneously by D2D discovery (transmission) and D2D communication(transmission) on the same subframe.

FIG. 13 is an example of CASE (2).

FIG. 14 is another modified example of ‘CASE (2)’.

FIG. 15 shows a power control method according to an embodiment of thepresent invention.

FIG. 16 shows again the sub-figure (b) of FIG. 9 for convenience.

FIG. 17 shows timing of D2D signal transmission and WAN UL signaltransmission.

FIG. 18 shows that a subframe k of a carrier c overlaps with a subframei of a carrier x.

FIG. 19 shows an example of a case where a sidelink subframe overlapswith a plurality of UL subframes.

FIG. 20 shows a method of determining UL TX power according to anembodiment of the present invention.

FIG. 21 is a block diagram showing a UE according to an embodiment ofthe present invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 1 shows a wireless communication system.

The wireless communication system may also be referred to as anevolved-UMTS terrestrial radio access network (E-UTRAN) or a long termevolution (LTE)/LTE-A system.

The E-UTRAN includes at least one base station (BS) 20 which provides acontrol plane and a user plane to a user equipment (UE) 10. The UE 10may be fixed or mobile, and may be referred to as another terminology,such as a mobile station (MS), a user terminal (UT), a subscriberstation (SS), a mobile terminal (MT), a wireless device, etc. The BS 20is generally a fixed station that communicates with the UE 10 and may bereferred to as another terminology, such as an evolved node-B (eNB), abase transceiver system (BTS), an access point, etc.

The BSs 20 are interconnected by means of an X2 interface. The BSs 20are also connected by means of an S1 interface to an evolved packet core(EPC) 30, more specifically, to a mobility management entity (MME)through S1-MME and to a serving gateway (S-GW) through S1-U.

The EPC 30 includes an MME, an S-GW, and a packet data network-gateway(P-GW). The MME has access information of the UE or capabilityinformation of the UE, and such information is generally used formobility management of the UE. The S-GW is a gateway having an E-UTRANas an end point. The P-GW is a gateway having a PDN as an end point.

Layers of a radio interface protocol between the UE and the network canbe classified into a first layer (L1), a second layer (L2), and a thirdlayer (L3) based on the lower three layers of the open systeminterconnection (OSI) model that is well-known in the communicationsystem. Among them, a physical (PHY) layer belonging to the first layerprovides an information transfer service by using a physical channel,and a radio resource control (RRC) layer belonging to the third layerserves to control a radio resource between the UE and the network. Forthis, the RRC layer exchanges an RRC message between the UE and the BS.

FIG. 2 is a diagram showing a wireless protocol architecture for a userplane. FIG. 3 is a diagram showing a wireless protocol architecture fora control plane. The user plane is a protocol stack for user datatransmission. The control plane is a protocol stack for control signaltransmission.

Referring to FIGS. 2 and 3, a PHY layer provides an upper layer with aninformation transfer service through a physical channel. The PHY layeris connected to a medium access control (MAC) layer which is an upperlayer of the PHY layer through a transport channel. Data is transferredbetween the MAC layer and the PHY layer through the transport channel.The transport channel is classified according to how and with whatcharacteristics data is transferred through a radio interface.

Data is moved between different PHY layers, that is, the PHY layers of atransmitter and a receiver, through a physical channel. The physicalchannel may be modulated according to an Orthogonal Frequency DivisionMultiplexing (OFDM) scheme, and use the time and frequency as radioresources.

The functions of the MAC layer include mapping between a logical channeland a transport channel and multiplexing and demultiplexing to atransport block that is provided through a physical channel on thetransport channel of a MAC Service Data Unit (SDU) that belongs to alogical channel. The MAC layer provides service to a Radio Link Control(RLC) layer through the logical channel.

The functions of the RLC layer include the concatenation, segmentation,and reassembly of an RLC SDU. In order to guarantee various types ofQuality of Service (QoS) required by a Radio Bearer (RB), the RLC layerprovides three types of operation mode: Transparent Mode (TM),Unacknowledged Mode (UM), and Acknowledged Mode (AM). AM RLC provideserror correction through an Automatic Repeat Request (ARQ).

The RRC layer is defined only on the control plane. The RRC layer isrelated to the configuration, reconfiguration, and release of radiobearers, and is responsible for control of logical channels, transportchannels, and PHY channels. An RB means a logical route that is providedby the first layer (PHY layer) and the second layers (MAC layer, the RLClayer, and the PDCP layer) in order to transfer data between UE and anetwork.

The function of a Packet Data Convergence Protocol (PDCP) layer on theuser plane includes the transfer of user data and header compression andciphering. The function of the PDCP layer on the user plane furtherincludes the transfer and encryption/integrity protection of controlplane data.

What an RB is configured means a process of defining the characteristicsof a wireless protocol layer and channels in order to provide specificservice and configuring each detailed parameter and operating method. AnRB can be divided into two types of a Signaling RB (SRB) and a Data RB(DRB). The SRB is used as a passage through which an RRC message istransmitted on the control plane, and the DRB is used as a passagethrough which user data is transmitted on the user plane.

If RRC connection is established between the RRC layer of UE and the RRClayer of an E-UTRAN, the UE is in the RRC connected state. If not, theUE is in the RRC idle state.

A downlink transport channel through which data is transmitted from anetwork to UE includes a broadcast channel (BCH) through which systeminformation is transmitted and a downlink shared channel (SCH) throughwhich user traffic or control messages are transmitted. Traffic or acontrol message for downlink multicast or broadcast service may betransmitted through the downlink SCH, or may be transmitted through anadditional downlink multicast channel (MCH). Meanwhile, an uplinktransport channel through which data is transmitted from UE to a networkincludes a random access channel (RACH) through which an initial controlmessage is transmitted and an uplink shared channel (SCH) through whichuser traffic or control messages are transmitted.

Logical channels that are placed over the transport channel and that aremapped to the transport channel include a broadcast control channel(BCCH), a paging control channel (PCCH), a common control channel(CCCH), a multicast control channel (MCCH), and a multicast trafficchannel (MTCH).

The physical channel includes several OFDM symbols in the time domainand several subcarriers in the frequency domain. One subframe includes aplurality of OFDM symbols in the time domain. An RB is a resourcesallocation unit, and includes a plurality of OFDM symbols and aplurality of subcarriers. Furthermore, each subframe may use specificsubcarriers of specific OFDM symbols (e.g., the first OFDM symbol) ofthe corresponding subframe for a physical downlink control channel(PDCCH), that is, an L1/L2 control channel. A Transmission Time Interval(TTI) is a unit time for subframe transmission.

The RRC state means whether or not the RRC layer of UE is logicallyconnected to the RRC layer of the E-UTRAN. A case where the RRC layer ofUE is logically connected to the RRC layer of the E-UTRAN is referred toas an RRC connected state. A case where the RRC layer of UE is notlogically connected to the RRC layer of the E-UTRAN is referred to as anRRC idle state. The E-UTRAN may check the existence of corresponding UEin the RRC connected state in each cell because the UE has RRCconnection, so the UE may be effectively controlled. In contrast, theE-UTRAN is unable to check UE in the RRC idle state, and a Core Network(CN) manages UE in the RRC idle state in each tracking area, that is,the unit of an area greater than a cell. That is, the existence ornon-existence of UE in the RRC idle state is checked only for each largearea. Accordingly, the UE needs to shift to the RRC connected state inorder to be provided with common mobile communication service, such asvoice or data.

When a user first powers UE, the UE first searches for a proper cell andremains in the RRC idle state in the corresponding cell. The UE in theRRC idle state establishes RRC connection with an E-UTRAN through an RRCconnection procedure when it is necessary to set up the RRC connection,and shifts to the RRC connected state. A case where UE in the RRC idlestate needs to set up RRC connection includes several cases. Forexample, the cases may include a need to send uplink data for a reason,such as a call attempt by a user, and to send a response message as aresponse to a paging message received from an E-UTRAN.

A Non-Access Stratum (NAS) layer placed over the RRC layer performsfunctions, such as session management and mobility management.

In the NAS layer, in order to manage the mobility of UE, two types ofstates: EPS Mobility Management-REGISTERED (EMM-REGISTERED) andEMM-DEREGISTERED are defined. The two states are applied to UE and theMME. UE is initially in the EMM-DEREGISTERED state. In order to access anetwork, the UE performs a process of registering it with thecorresponding network through an initial attach procedure. If the attachprocedure is successfully performed, the UE and the MME become theEMM-REGISTERED state.

In order to manage signaling connection between UE and the EPC, twotypes of states: an EPS Connection Management (ECM)-IDLE state and anECM-CONNECTED state are defined. The two states are applied to UE andthe MME. When the UE in the ECM-IDLE state establishes RRC connectionwith the E-UTRAN, the UE becomes the ECM-CONNECTED state. The MME in theECM-IDLE state becomes the ECM-CONNECTED state when it establishes S1connection with the E-UTRAN. When the UE is in the ECM-IDLE state, theE-UTRAN does not have information about the context of the UE.Accordingly, the UE in the ECM-IDLE state performs procedures related toUE-based mobility, such as cell selection or cell reselection, without aneed to receive a command from a network. In contrast, when the UE is inthe ECM-CONNECTED state, the mobility of the UE is managed in responseto a command from a network. If the location of the UE in the ECM-IDLEstate is different from a location known to the network, the UE informsthe network of its corresponding location through a tracking area updateprocedure.

Now, a device-to-device (D2D) operation is described. In 3GPP LTE-A, aservice related to the D2D operation is called a proximity based service(ProSe). Hereinafter, the ProSe is the same concept as the D2Doperation, and the ProSe and the D2D operation may be used withoutdistinction. Now, the ProSe is described.

The ProSe includes ProSe direction communication and ProSe directdiscovery. The ProSe direct communication is communication performedbetween two or more proximate UEs. The UEs may perform communication byusing a protocol of a user plane. A ProSe-enabled UE implies a UEsupporting a procedure related to a requirement of the ProSe. Unlessotherwise specified, the ProSe-enabled UE includes both of a publicsafety UE and a non-public safety UE. The public safety UE is a UEsupporting both of a function specified for a public safety and a ProSeprocedure, and the non-public safety UE is a UE supporting the ProSeprocedure and not supporting the function specified for the publicsafety.

The ProSe direct discovery is a procedure used when the ProSe-enabled UEdiscovers another proximate ProSe-enabled UE. In this case, onlycapability of the two ProSe-enabled UEs is used. EPC-level ProSediscovery is a procedure in which an EPC determines whether twoProSe-enabled UEs are in proximity to each other and repots theirproximity to the two ProSe-enabled UEs.

Hereinafter, for convenience, the ProSe direct communication may bereferred to as D2D communication, and the ProSe direct discovery may bereferred to as D2D discovery.

FIG. 4 shows a reference structure for a ProSe.

Referring to FIG. 4, the reference structure for the ProSe includes anE-UTRAN, an EPC, a plurality of UEs including a ProSe application, aProSe application (APP) server, and a ProSe function.

The EPC represents an E-UTRAN core network structure. The EPC mayinclude an MME, an S-GW, a P-GW, a policy and charging rules function(PCRF), a home subscriber server (HSS), or the like.

The ProSe APP server is a user having ProSe capability for creating anapplication function. The ProSe APP server may communicate with anapplication included in the UE. The application included in the UE mayuse the ProSe capability for creating the application function.

The ProSe function may include at least one of the following functions,but is not necessarily limited thereto.

-   -   Interworking via a reference point towards the 3rd party        applications.    -   Authorization and configuration of the UE for discovery and        direct communication    -   Enable the functionality of the EPC level ProSe discovery    -   ProSe related new subscriber data and handling of data storage,        and also handling of ProSe identities    -   Security related functionality    -   Provide control towards the EPC for policy related functionality    -   Provide functionality for charging (via or outside of EPC, e.g.,        offline charging)

Hereinafter, a reference point and a reference interface in thereference structure for the ProSe are described.

-   -   PC1: a reference point between the ProSe application included in        the UE and the ProSe-application included in the ProSe APP        server. This is used to define a signaling requirement in an        application level.    -   PC2: a reference point between the ProSe APP server and the        ProSe function. This is used to define an interaction between        the ProSe APP server and the ProSe function. An application data        update of a ProSe database of the ProSe function may be one        example of the interaction.    -   PC3: a reference point between the UE and the ProSe function.        This is used to define an interaction between the UE and the        ProSe function. A configuration for ProSe discovery and        communication may be one example of the interaction.    -   PC4: a reference point between the EPC and the ProSe function.        This is used to define an interaction between the EPC and the        ProSe function. The interaction may exemplify a case where a        path is established for 1:1 communication between UEs or a case        where a ProSe service is authenticated for real-time session        management or mobility management.    -   PC5: a reference point for using a control/user plane for        discovery, communication, relay, and 1:1 communication between        UEs.    -   PC6: a reference point for using a function such as ProSe        discovery between users belonging to different PLMNs.    -   SGi: This may be used for application data and application-level        control information exchange.

The D2D operation may be supported in both of a case where the UEreceives a service inside coverage of a network (cell) or a case wherethe UE is outside the coverage of the network.

FIG. 5 shows examples of cell coverage deployment with UEs performing aD2D operation.

Referring to FIG. 5(a), UEs A and B may be both located outside cellcoverage. Referring to FIG. 5(b), the UE A may be located inside thecell coverage, and the UE B may be located outside the cell coverage.Referring to FIG. 5(c), the UEs A and B may be both located inside asingle cell coverage. Referring to FIG. 5(d), the UE A may be locatedinside coverage of a 1st cell, and the UE B may be located insidecoverage of a 2nd cell.

The D2D operation may be performed between UEs which exist in variouslocations as shown in FIG. 5.

<Radio resource allocation for D2D communication (ProSe directioncommunication)>

At least one of the following two modes may be used to allocateresources for the D2D communication.

1. Mode 1

The mode 1 is a mode in which a resource for ProSe directioncommunication is scheduled from a base station. A UE must be in anRRC_CONNECTED state to transmit data according to the mode 1. The UErequests the base station to transmit a resource, and the base stationschedules a resource for scheduling allocation or data transmission. TheUE may transmit a scheduling request to the base station, and maytransmit a ProSe buffer status report (BSR). On the basis of the ProSeBSR, the base station determines that the UE has data for ProSedirection communication and that a resource for transmitting the data isnecessary.

2. Mode 2

The mode 2 is a mode in which a UE directly selects a resource. The UEselects a resource for ProSe direct communication directly from aresource pool. The resource pool may be configured by a network or maybe predetermined.

Meanwhile, if the UE has a serving cell, that is, if the UE is in anRRC_CONNECTED state with respect to a base station or is located in aspecific cell in an RRC_IDLE state, it is considered that the UE existsinside coverage of the base station.

If the UE exists outside the coverage, only the mode 2 may be applied.If the UE exists inside the coverage, the mode 1 or the mode 2 may beused according to a configuration of the base station.

If there is no other exceptional condition, the UE may change the modefrom the mode 1 to the mode 2 or from the mode 2 to the mode 1 only whenit is configured by the base station.

<D2D Discovery (ProSe Direct Discovery)>

The D2D discovery is a procedure used when a ProSe-enabled UE discoversanother proximate ProSe-enabled UE, and may also be referred to as ProSedirect discovery. Information used in the ProSe direct discovery ishereinafter referred to as discovery information.

The PC5 interface may be used for the D2D discovery. The PC5 interfaceconsists of a MAC layer, a PHY layer, and a ProSe protocol layer whichis a higher layer. The higher layer (i.e., ProSe protocol) deals with agrant for announcement and monitoring of the discovery information, andthe content of the discovery information is transparent to an accessstratum (AS). The ProSe protocol allows only valid discovery informationto be delivered to the AS for the announcement. The MAC layer receivesthe discovery information from the higher layer (i.e., ProSe protocol).An IP layer is not used for discovery information transmission. The MAClayer determines a resource used to announce the discovery informationreceived from the higher layer. The MAC layer creates a MAC protocoldata unit (PDU) for carrying the discovery information, and sends it tothe PHY layer. A MAC header is not added.

For the discovery information announcement, there are two types ofresource allocation.

1. Type 1

As a method in which resources for announcement of discovery informationare allocated not in a UE-specific manner, a base station provides aresource pool configuration for the discovery information announcementto UEs. This configuration may be signaled in a broadcast manner bybeing included in a system information block (SIB). Alternatively, theconfiguration may be provided by being included in a UE-specific RRCmessage. Alternatively, the configuration may be broadcast signaling ofa different layer or UE-specific signaling, other than the RRC message.

The UE autonomously selects a resource from an indicated resource pool,and announces the discovery information by using the selected resource.The UE may announce the discovery information by using a resourcerandomly selected during each discovery period.

2. Type 2

This is a method in which resources for announcement of discoveryinformation are allocated in a UE-specific manner. A UE in anRRC_CONNECTED state may request a base station to provide a resource forthe discovery signal announcement via an RRC signal. The base stationmay allocate the resource for the discovery signal announcement via theRRC signal. A resource for discovery signal monitoring may be allocatedwithin a resource pool configured to the UEs.

For a UE in an RRC_IDLE state, 1) the base station may report a type-1resource pool for the discovery signal announcement via an SIB. When theProSe direct discovery is allowed, UEs use the ProSe direct discoveryfor the discovery information announcement in the RRC_IDLE state.Alternatively, 2) the base station may announce that the base stationsupports the ProSe direct discovery via the SIB but may not provide aresource for the discovery information announcement. In this case, theUE must enter the RRC_CONNECTED state for the discovery informationannouncement.

For the UE in the RRC_CONNECTED state, the base station may determinewhether the UE will use a type-1 resource pool or a type-2 resource poolfor the discovery information announcement via the RRC signal.

FIG. 6 is an exemplary embodiment of a D2D discovery procedure.

Referring to FIG. 6, it is assumed that a UE A and a UE B operate aProSe-enabled application, and are configured in the application as arelation of ‘friend’, that is, a relation capable of allowing D2Dcommunication with each other. Hereinafter, the UE B may be expressed asa ‘friend’ of the UE A. The application may be, for example, a socialnetworking program. ‘3GPP layers’ correspond to functions of anapplication for using a ProSe discovery service, specified by 3GPP.

ProSe direct discovery between the UEs A and B may be subjected to thefollowing procedure.

1. First, the UE A performs regular application layer communication withan application server. This communication is based on an applicationprogramming interface (API).

2. A ProSe-enabled application of the UE A receives a list of anapplication layer ID having a relation of ‘friend’. The applicationlayer ID may generally have a form of a network access ID. For example,the application layer ID of the UE A may have a form of“adam@example.com”.

3. The UE A requests for private expressions codes for a user of the UEA and private expressions codes for a friend of the user.

4. 3GPP layers transmit an expressions codes request to a ProSe server.

5. The ProSe server maps application layer IDs provided from an operatoror a third-party application server to the private expressions codes.For example, an application layer ID such as “adam@example.com” may bemapped to private expressions codes such as “GTER543$#2FSJ67DFSF”. Thismapping may be performed on the basis of parameters (e.g., a mappingalgorithm, a key value, etc.) received from an application server of anetwork.

6. The ProSe server responds to the 3GPP layers with the derivedexpressions codes. The 3GPP layers announce to a ProSe-enabledapplication a successful reception of expressions codes for therequested application ID. In addition, a mapping table between theapplication layer ID and the expressions codes is created.

7. The ProSe-enabled application requests the 3GPP layers to start adiscovery procedure. That is, the discovery is attempted when one of theprovided ‘friends’ exists in proximity to the UE A and directcommunication is possible. The 3GPP layers announce private expressionscodes (i.e., “GTER543$#2FSJ67DFSF” which is private expressions codes of“adam@example.com” in the above example) of the UE A. This ishereinafter referred to as ‘announce’. Mapping between the privateexpressions codes and the application layer ID of the application may beknown to and performed by only ‘friends’ who have received such amapping relation in advance.

8. It is assumed that the UE B is operating the same ProSe-enabledapplication as the UE A, and has executed the aforementioned steps 3 to6. 3GPP layers in the UE B may execute the ProSe discovery.

9. When the UE B receives the aforementioned announce from the UE A, theUE B determines whether private expressions codes included in theannounce are known to the UE B or are mapped to an application layer ID.As described in step 8, since steps 3 to 6 have already been executed,the UE B also knows private expressions codes for the UE A, mappingbetween the private expressions codes and the application layer ID, anda corresponding application. Therefore, the UE B may discover the UE Afrom the announce of the UE A. 3GPP layers in the UE B announce to aProSe-enabled application that “adam@example.com” is discovered.

In FIG. 6, the discovery procedure is described by considering all ofthe UEs A and B, the ProSe server, the application server, etc. From anaspect of an operation between the UEs A and B, the UE A transmits asignal called an announce (this process may be referred to as anannouncement), and the UE B discovers the UE A by receiving theannounce. That is, from an aspect that an operation directly related toanother UE among operations performed by each UE is only one step, thediscovery procedure of FIG. 6 may be referred to as a single-stepdiscovery procedure.

FIG. 7 shows another embodiment of a D2D discovery procedure.

In FIG. 7, it is assumed that UEs 1 to 4 are UEs included in a specificgroup communication system enablers (GCSE) group. It is assumed that theUE 1 is a discoverer, and the UEs 2, 3, and 4 are discoverees. A UE 5 isa UE irrelevant to the discovery procedure.

The UE 1 and the UEs 2 to 4 may perform the following operation in thediscovery procedure.

First, the UE 1 broadcasts a targeted discovery request message(hereinafter, also simply referred to as a discovery request message orM1) to discover whether any UE included in the GCSE group exists inproximity. The targeted discovery request message may include a uniqueapplication group ID or layer-2 group ID of the specific GCSE group.Further, the targeted discovery request message may include a unique IDof the UE 1, i.e., an application private ID. The targeted discoveryrequest message may be received by the UEs 2, 3, 4, and 5.

The UE 5 does not transmit any response message. On the other hand, theUEs 2, 3, and 4 included in the GCSE group transmit a targeted discoveryresponse message (hereinafter, also simply referred to as a discoveryresponse message or M2) in response to the targeted discovery requestmessage. The targeted discovery response message may include a uniqueapplication private ID of a UE which transmits this message.

In an operation performed between UEs in the ProSe discovery proceduredescribed in FIG. 7, a discoverer (i.e., the UE 1) transmits a targeteddiscovery request message, and receives a targeted discovery responsemessage in response thereto. Further, upon receiving a targeteddiscovery request message, a discoveree (e.g., the UE 2) also transmitsa targeted discovery response message in response thereto. Therefore,each UE performs an operations of two steps. In this aspect, the ProSediscovery procedure of FIG. 7 may be referred to as a 2-step discoveryprocedure.

In addition to the discovery procedure described in FIG. 7, if the UE 1(i.e., discoverer) transmits a discovery confirm message (hereinafter,also simply referred to as M3) in response to a targeted discoveryresponse message, this may be referred to as a 3-step discoveryprocedure.

Meanwhile, a UE supporting a D2D operation may provide relayfunctionality to another network node (e.g., another UE or basestation).

FIG. 8 shows an example of a UE for providing relay functionality.

Referring to FIG. 8, a UE2 153 plays a role of a relay between a basestation 151 and a UE1 152. That is, the UE2 153 may be a network nodewhich plays a role of a relay between the network 151 and the UE1 152located outside a network coverage 154. A D2D operation may be performedbetween the UE1 152 and the UE2 153, and the conventional cellularcommunication (or wide area network (WAN) communication) may beperformed between the UE2 153 and the network 151. In FIG. 8, since theUE1 152 is located outside the network coverage, communication with thenetwork 151 cannot be performed if the UE2 153 does not provide therelay functionality.

Now, the present invention is described.

The present invention proposes a method of effectively determiningtransmit power when a UE for performing a D2D operation (hereinafter,such a UE may be called a “D2D UE”) transmits a D2D signal. Herein, theD2D operation may include D2D discovery and D2D communication. This hasbeen described above. The D2D communication implies communicationperformed by a UE to directly exchange data with other UEs by using awireless channel. Hereinafter, the D2D discovery may be simply referredto as discovery. In general, the UE implies a UE used by a user.However, when network equipment such as a base stationtransmits/receives a signal according to a communication scheme betweenUEs, the network equipment may also be considered as a type of the UE.

First, acronyms used in the present specification are described.

(1) PSBCH (Physical Sidelink Broadcast CHannel): physical sidelinkbroadcast channel.

(2) PSCCH (Physical Sidelink Control CHannel): physical sidelink controlchannel.

(3) PSDCH (Physical Sidelink Discovery CHannel): physical sidelinkdiscovery channel.

(4) PSSCH (Physical Sidelink Shared CHannel): physical sidelink sharedchannel.

(5) SSS (Sidelink Synchronization Signal): sidelink synchronizationsignal. SSS may also be expressed as SLSS. The SSS may include PSSS andSSSS. A.PSSS (Primary Sidelink Synchronization Signal): primary sidelinksynchronization signal, B.

SSSS (Secondary Sidelink Synchronization Signal): secondary sidelinksynchronization signal.

Hereinafter, for convenience of explanation, a proposed method isdescribed on the basis of a 3GPP LTE/LTE-A system. However, a scope ofsystems to which the proposed method is applied can also be extended toother systems in addition to the 3GPP LTE/LTE-A system.

A UE may calculate transmit power as follows in association withPSSCH/PSCCH/PSDCH/PSSS/SSSS in a subframe in which a D2D operation isperformed.

1) PSSCH power control

In case of a sidelink transmission mode 1 and a PSCCH period i, if a TPCfield of a sidelink grant for the PSCCH period i is set to 0, it isgiven as P_(PSSCH)=P_(CMAX,PSSCH). If the TPC field for the sidelinkgrant for the PSCCH period i is set to 1, P_(PSSCH) is given by thefollowing equation.P _(PSSCH)=min{P _(CMAX,PSSCH),10 log₁₀(M _(PSSCH))+P_(O_SSCH,1)+α_(SSCH,1)·PL} [dBm]  [Equation 1]

In the above equation, P_(CMAX,PSSCH) is a value of P_(CMAX,c)determined by the UE as to an uplink subframe corresponding to asidelink subframe in which a PSSCH is transmitted. M_(PSSCH) is a bandof a PSSCH resource allocation expressed by the number of resourceblocks. PL denotes a path loss value. P_(O_PSSCH,1) and α_(PSSCH,1) arevalues provided by higher layer parameters.

For a sidelink transmission mode 2, P_(PSSCH) is given by the followingequation.P _(PSSCH)=min{P _(CMAX,PSSCH),10 log(M _(PSSCH))+P_(O_PSSCH,2)+α_(PSSCH,2)·PL} [dBm]  [Equation 2]

In the above equation, P_(CMAX,PSSCH) is a value of P_(CMAX,c)determined by the UE as to an uplink subframe corresponding to asidelink subframe in which a PSSCH is transmitted. M_(PSSCH) is a bandof a PSSCH resource allocation expressed by the number of resourceblocks. PL denotes a path loss value. P_(O_PSSCH,2) and α_(PSSCH,2) arevalues provided by higher layer parameters.

2) PSCCH Power Control

In case of a sidelink transmission mode 1 and a PSCCH period i, if a TPCfield of a sidelink grant for the PSCCH period i is set to 0, it isgiven as P_(PSCCH)=P_(CMAX,PSCCH). If the TPC field for the sidelinkgrant for the PSCCH period i is set to 1, P_(PSCCH) is given by thefollowing equation.P _(PSCCH)=min{P _(CMAX,PSCCH),10 log₁₀(M _(PSCCH))+P_(O_PSCCH,1)+α_(PSCCH,i)·PL} [dBm]  [Equation 3]

In the above equation, P_(CMAX,PSCCH) is a value of P_(CMAX,c)determined by the UE as to an uplink subframe corresponding to asidelink subframe in which a PSCCH is transmitted. M_(PSCCH) is 1, andPL denotes a path loss value. P_(O_PSCCH,1) and α_(PSCCH,1) are valuesprovided by higher layer parameters.

For a sidelink transmission mode 2, P_(PSCCH) is given by the followingequation.P _(PSCCH)=min{P _(CMAX,PSCCH),10 log₁₀(M _(PSCCH))+P_(O_PSCCH,2)+α_(PSCCH,2)·PL} [dBm]  [Equation 4]

In the above equation, P_(CMAX,PSCCH) is a value of P_(CMAX,c)determined by a higher layer (or determined by the UE as to an uplinksubframe corresponding to a sidelink subframe in which a PSCCH istransmitted). M_(PSCCH) is 1, and PL denotes a path loss value.P_(O_PSCCH,2) and α_(PSCCH,2) are values provided by higher layerparameters.

3) PSDCH Power Control

For a sidelink discovery, P_(PSDCH) is given by the following equation.P _(PSDCH)=min{P _(CMAX,PSDCH),10 log₁₀(M _(PSDCH))+P_(O_PSDCH,1)+α_(PSDCH,1)·PL} [dBm]  [Equation 5]

In the above equation, P_(CMAX,PSDCH) is a value of P_(CMAX,c)determined by the UE as to an uplink subframe corresponding to asidelink subframe in which a PSDCH is transmitted. M_(PSDCH) is 2, andPL denotes a path loss value. P_(O_PSDCH,1) and α_(PSDCH,1) are valuesprovided by higher layer parameters.

4) Sidelink Synchronization Signal (SSS) Power Control

In a sidelink, if transmit power used to transmit a primarysynchronization signal (PSSS) and a secondary synchronization signal(SSSS) is denoted by P_(PSSS), it is given as P_(PSSS)=P_(CMAX,PSSS)when a sidelink transmission mode 1 is set to a UE, a sidelinksynchronization signal is transmitted in a PSCCH period i, and a TPCfield of a sidelink grant for the PSCCH period i is set to 0. Otherwise,P_(PSSS) is given by the following equation.P _(PSSS)=min{P _(CMAX,PSSS),10 log₁₀(M _(PSSS))+P_(O_PSSS)+α_(PSSS)·PL} [dBm]  [Equation 6]

In the above equation, P_(CMAX,PSSS) is a value of P_(CMAX,c) determinedby the UE as to an uplink subframe corresponding to a sidelink subframein which a sidelink synchronization signal (SSS) is transmitted.P_(O_PSSS) and α_(PSSS) are values provided by higher layer parameters,and are related to a corresponding SSS resource configuration.

Meanwhile, values P_(CMAX) and P_(CMAX,c) used to determine uplinksignal transmit power in an uplink subframe of a WAN (i.e., an uplinksubframe used in uplink transmission of a WAN such as LTE/LTE-A) may bedefined or calculated as follows.

The UE is allowed to autonomously configure P_(CMAX,c) in a specificrange as maximum output power configured for a serving cell. P_(CMAX,c)may be configured within a specific range as shown in the followingequation.P _(CMAX_L,c) ≤P _(CMAX,c) ≤P _(CMAX_H,c)  [Equation 7]

In the above equation, P_(CMAX,L,c) and P_(CMAX,H,c) are given by thefollowing equation.P _(CMAX_L,c)=MIN {P _(EMAX,c) −□T _(C,c) ,P _(PowerClass)−MAX(MPR_(c)+A-MPR_(c) +ΔT _(IB,c) +□T _(C,c) ,P-MPR_(c))}P _(CMAX_H,c)=MIN {P _(EMAX,c) ,P _(PowerClass)}  [Equation 8]

In the above equation, P_(EMAX,c) is a value provided by IE P-Max as aninformation element (IE) for a serving cell c. The IE P-Max may beincluded in an RRC message. P_(PowerClass) is maximum UE power in whicha tolerance is not considered. MPR_(c) denotes a maximum power reductionvalue for the serving cell c, and A-MPR_(c) denotes an additionalmaximum power reduction value for the serving cell c. T_(IB,c) denotesan additional tolerance for the serving cell. T_(C,c) is 1.5 dB or 0 dB.P-MPR_(c) is an allowed maximum output power reduction. MIN {A, B}denotes a smaller value between A and B.

For each subframe, P_(CMAX,L,c) for the serving cell c is calculated foreach slot, and a minimum value among values P_(CMAX,L,c) calculated ineach of two slots in the subframe is applied to the entirety of thesubframe. The UE does not exceed P_(PowerClass) in any time period.

Meanwhile, if the measured ‘configured maximum output power’ isP_(UMAX,c), P_(UMAX,c) is in the following range.P _(CMAX_L,c)−MAX{T _(L) ,T(P _(CMAX_L,c))}≤P _(UMAX,c) ≤P _(CMAX_H,c)+T(P _(CMAX_H,c))  [Equation 9]

In the above equation, MAX {A, B} denotes a greater value between A andB, and T(P_(CMAX,c)) may be defined by the following table.

TABLE 1 Tolerance P_(CMAX,c) T(P_(CMAX, c)) (dBm) (dB)  23 < P_(CMAX, c)≤ 33 2.0  21 ≤ P_(CMAX, c) ≤ 23 2.0 20 ≤ P_(CMAX, c) < 21 2.5 19 ≤P_(CMAX, c) < 20 3.5 18 ≤ P_(CMAX, c) < 19 4.0 13 ≤ P_(CMAX, c) < 18 5.0 8 ≤ P_(CMAX, c) < 13 6.0 −40 ≤ P_(CMAX, c) < 8  7.0

According to a modulation and a channel bandwidth, a maximum powerreduction (MPR) allowed for maximum output power may be defined by thefollowing table.

TABLE 2 Channel bandwidth/Transmission bandwidth (N_(RB)) Modulation 1.4MHz 3.0 MHz 5 MHz 10 MHz 15 MHz 20 MHz MPR (dB)QPSK >5 >4 >8 >12 >16 >18 ≤1 16 QAM ≤5 ≤4 ≤8 ≤12 ≤16 ≤18 ≤1 16QAM >5 >4 >8 >12 >16 >18 ≤2

The network announces a requirement to be additionally satisfied in aspecific deployment scenario to the UE by signaling an additionaladjacent channel leakage power ratio (ACLR) and a spectrum emissionrequirement. The ACLR denotes a ratio of average power filtered at acenter of an allocated channel frequency and average power filtered at acenter of an adjacent channel frequency. To satisfy such an additionalrequirement, an additional maximum power reduction (A-MPR) may beallowed.

In an uplink carrier aggregation which aggregates and uses a pluralityof carriers in an uplink, the UE is allowed to configure P_(CMAX,c)which is maximum output power for the serving cell c included in theplurality of carriers and P_(CMAX) which is maximum output power for allof the plurality of carriers.

In an inter-band uplink carrier aggregation, P_(CMAX) may be determinedwithin a specific range as shown in the following equation.P _(CMAX_L) ≤P _(CMAX) ≤P _(CMAX_H)  [Equation 10]

In the above equation, P_(CMAX_L) and P_(CMAX_H) may be determined bythe following equation.P _(CMAX_L)=MIN{10 log₁₀Σ MIN[p _(EMAX,c)/(□t _(C,c)),p_(PowerClass)/(mpr_(c′) a-mpr_(c′) □t _(C,c) ·□t _(IB,c)),p_(PowerClass)/pmpr_(c)],P _(PowerClass)}P _(CMAX_H)=MIN{10 log₁₀ Σp _(EMAX,c) ,P _(PowerClass)}  [Equation 11]

In the above equation, p_(EMAX,c) is a linear value of P_(EMAX,c) givenby IE P-Max for the serving cell c.

P_(PowerClass) is maximum UE power in which a tolerance is notconsidered, and p_(PowerClass) is a linear value of P_(PowerClass).mpr_(c) and a-mpr_(c) are linear values of MPR_(c) and A-MPR_(c).pmpr_(c) is a linear value of P-MPR_(c). □t_(C,c) is a linear value of□T_(C,c), and is 1.41 or 0. □t_(IB,c) is a linear value of □T_(IB,c).

Meanwhile, in an intra-band uplink carrier aggregation, P_(CMAX_L) andP_(CMAX_H) may be determined as shown in the following equation.P _(CMAX_L)=MIN{10 log₁₀ Σp _(EMAX,c) −□T _(C) ,P_(PowerClass)−MAX(MPR+A-MPR+ΔT _(IB,c) +ΔT _(C) ,P-MPR)}P _(CMAX_H)=MIN{10 log₁₀ Σp _(EMAX,c) ,P _(PowerClass)}  [Equation 12]

In the above equation, p_(EMAX,c) is a linear value of P_(EMAX,c) givenby IE P-Max for the serving cell c. P_(PowerClass) is maximum UE powerin which a tolerance is not considered. MPR denotes a maximum powerreduction value, and A-MPR denotes an additional maximum power reductionvalue. T_(IB,c) denotes an additional tolerance for the serving cell c.ΔT_(C) is a highest value among values ΔT_(C,c), and ΔT_(C,c) is 1.5 dBis 0 dB. P-MPR is a power management term for the UE.

For each subframe, P_(CMAX,L) is calculated per slot, and a minimumvalue among values P_(CMAX,L) calculated in each of two slots in thesubframe is applied to the entirety of the subframe. The UE does notexceed P_(PowerClass) in any time period.

If a plurality of timing advance groups (TAGs) is configured to the UE,and if a first symbol of transmission for another serving cell belongingto another TAG partially overlaps in a subframe i+1 when the UE performstransmission for any serving cell belonging to one TAG in a subframe i,the UE may apply a maximum value of P_(CMAX_L) for the subframes i andi+1 to the overlapped part. The UE does not exceed P_(PowerClass) in anytime period.

For an intra-band contiguous carrier aggregation, an MPR may be given asfollows.

TABLE 3 CA bandwidth Class C 100 RB + 25 RB + 50 RB + 75 RB + 75 RB +100 Modulation 100 RB 100 RB 75 RB 100 RB RB MPR (dB) QPSK >8 and >12and >16 and >16 and >18 and ≤1 ≤25 ≤50 ≤75 ≤75 ≤100QPSK >25 >50 >75 >75 >100 ≤2 16 QAM  ≤8 ≤12  ≤16  ≤16   ≤18 ≤1 16 QAM >8and >12 and >16 and >16 and >18 and ≤2 ≤25 ≤50 ≤75 ≤75 ≤100 16QAM >25 >50 >75 >75 >100 ≤3

It is described an example of determining transmit power in a dualconnectivity state which indicates a state where the UE is connected totwo different cells.

It is assumed that maximum output power for the serving cell of a cellgroup i(i=1,2) is denoted by P_(CMAX,c,i). In this case, P_(CMAX,c,i)may be configured in the following range.P _(CMAX_L,c,i) ≤P _(CMAX,c,i) ≤P _(CMAX_H,c,i)  [Equation 13]

Meanwhile, total maximum output power P_(CMAX) of the UE is determinedas followingP _(CMAX_L) ≤P _(CMAX) ≤P _(CMAX_H)  [Equation 14]

If a dual connectivity is configured to the UE, subframes for one cellgroup may overlap with subframes for another cell group.

If simultaneous transmission occurs between uplink serving cells of thecell groups, P_(CMAX_L) and P_(CMAX_H) are determined similarly to aninter-band carrier aggregation.

If the dual connectivity is configured to the UE and if transmission ina subframe p for a 1^(st) serving cell of a 1^(st) cell group partiallyoverlaps with transmission in a subframe q+1 for a 2^(nd) serving cellof a 2^(nd) cell group (it may overlap in a part of a 1^(st) symbol ofthe subframe q+1), the UE may apply a smallest P_(CMAX_L) to theoverlapped part between subframe pairs (p,q) and (p+1,q+1). The UE doesnot exceed P_(PowerClass) in any time period.

Methods described hereinafter can be used to determine/allocate transmitpower related to D2D signal transmission in a subframe for transmittinga D2D signal (hereinafter, also expressed as a D2D subframe (SF)). Inthe following methods, D2D signal transmit power must be constant in oneD2D SF, and may be interpreted as not having an effect on determining oftransmit power of a WAN uplink signal transmitted at the same time or apartially overlapping time on different carriers. That is, it may beinterpreted that a WAN uplink signal has a higher priority than a D2Dsignal in terms of power allocation.

A D2D signal transmitted at a specific time may determine transmit poweron the basis of the following rule. Hereinafter, for convenience ofexplanation, the following cases are assumed.

‘CASE (1)’ shows a case where a time synchronization related to a D2Dsignal transmission subframe (this may be referred to as a “D2D TX SF”)on a Cell # A is identical to a time synchronization related to asubframe for transmitting a WAN uplink signal (this may be referred toas a “WAN UL TX SF”) on a Cell # B.

‘CASE (2)’ shows a case where a time synchronization related to a D2D TXSF on a Cell # A is different from a time synchronization related to aWAN UL TX SF on a Cell # B. A difference level may be within apre-defined or signaled threshold. Further, for example, since the Cell# A and the Cell # B belong to different timing advance groups (TAGs) in‘CASE (2)’, it may be interpreted as a case where an SF # Q which is theD2D TX SF of the Cell # A partially overlaps with an SF #(P+1) which isthe WAN UL TX SF of the Cell # B.

FIG. 9 exemplifies the aforementioned ‘CASE (1)’ and ‘Case (2)’.

Referring to the sub-figure (a) of FIG. 9, an SF # Q of a Cell # A andan SF # P of a Cell # B are aligned temporally. That is, timingsynchronization is achieved in the SF # Q of the Cell # A and the SF # Pof the Cell # B.

Referring to the sub-figure (b) of FIG. 9, an SF # Q of a Cell # A andan SF # P of a Cell # B are not aligned temporally. Unlike thesub-figure (a) of FIG. 9, the SF # Q of the Cell # A partially overlapswith an SF # P+1 of the Cell # B.

The proposed methods of the present invention are also applicableextensively to other cases, for example, a case where the SF # Q whichis the D2D TX SF on the Cell # A (or a D2D cell/carrier) leads the SF #P which is the WAN TX SF on the Cell # B (or a WAN UL cell(carrier)) ona time domain, and/or a case where the SF # P which is the WAN UL TX SFon the Cell # B (or a WAN UL cell/carrier) leads the SF # Q which is theD2D TX SF on the Cell # A (or a D2D cell(carrier)) on the time domain.

Hereinafter, for convenience of explanation, an SF index ‘Q (/(Q+1))’ ofthe Cell # A may be assumed as ‘K (or (K+1)) (/(K+1))’, and an SF index‘P (/(P+1))’ of the Cell # B may be assumed as ‘K (or (K+1)) (/(K+1))’.

Further, the proposed methods of the present invention may be limitedlyapplied only when a discovery signal is transmitted in practice and/orwhen a signal is transmitted through D2D communication.

[Proposed method #1] When an operation of transmitting a discoverysignal is performed by a UE which intends to perform a D2D operation inan SF # N of a Cell # C, a value P_(CMAX,C)(N) (and/or P_(CMAX)(N)) tobe used when determining discovery signal TX power may be calculated bysubstituting a maximum (discovery) TX power value indicated by‘discMaxTxPower-r12’ related to the Cell # C to a parameter P_(EMAX,C).

Herein, the ‘discMaxTxPower-r12’ is a parameter used to calculatemaximum TX power when a UE configured as a specific range classtransmits a discovery signal (ProSe direct discovery), and may indicatemaximum TX power which must not be exceeded by the UE configured as thespecific range class when the discovery signal is transmitted insidecoverage of a corresponding cell.

FIG. 10 shows a discovery signal transmission method of a UE accordingto an embodiment of the present invention.

Referring to FIG. 10, a UE #1 receives power information‘discMaxTxPower’ for discovery signal transmission from a network(S101). The network may be, for example, a serving cell of the UE #1,and the UE #1 may exist inside coverage of the serving cell. The powerinformation discMaxTxPower may be received via not a system informationblock for receiving power information for D2D communication but viaother system information blocks. For example, power information P-Maxfor D2D communication may be received via an SIB 1, and the powerinformation discMaxTxPower may be received via other system informationblocks.

The following table is an example of the power informationdiscMaxTxPower for discovery signal transmission.

TABLE 4 -- ASN1START SL-DiscTxPowerInfoList-r12 ::= SEQUENCE (SIZE(maxSL-DiscPowerClass-r12)) OF SL-DiscTxPowerInfo-r12SL-DiscTxPowerInfo-r12 ::=       SEQUENCE {    discMaxTxPower-r12         P-Max,    ... } -- ASN1STOP

In the above table, discMaxTxPower-r12 may be provided plural in number,and in this case, first one may relate to a UE having a short rangeclass, second one may relate to a UE having a medium range class, andthird one may relate to a UE having a long range class. A range class isconfigured to the UE, and the range class may indicate any one of short,medium, and long. In this case, the power information discMaxTxPower mayindicate maximum transmit power which must not be exceeded when the D2Ddiscovery signal is transmitted according to the range class configuredto the UE.

The UE #1 determines TX power for the discovery signal transmission onthe basis of the power information for the discovery signal transmission(S102).

For example, maximum output power P_(CMAX,c) for discovery signaltransmission at a serving cell c may be determined as shown in thefollowing equation.P _(CMAX_L,c) ≤P _(CMAX,c) ≤P _(CMAX_H,c)  [Equation 15]

In the above equation, P_(CMAX,L,c) and P_(CMAX,H,c) are given by thefollowing equation.P _(CMAX_L,c)=MIN{P _(EMAX,c) −ΔT _(C,c) ,P _(PowerClass)−MAX(MPR_(c)+A-MPR_(c) +ΔT _(IB,c) +ΔT _(C,c) +ΔT _(ProSe) ,P-MPR_(c))}P _(CMAX_H,c)=MIN {P _(EMAX,c) ,P _(PowerClass)}  [Equation 16]

In the above equation, P_(EMAX,c) is not IE P-Max as an informationelement (IE) for a serving cell c but a value provided by theaforementioned power information ‘discMaxTxPower’ for discovery signaltransmission. The ‘discMaxTxPower’ may be provided via an RRC signal.P_(PowerClass) is maximum UE power in which a tolerance is notconsidered. MPR_(c) denotes a maximum power reduction value for theserving cell c, and A-MPR_(c) denotes an additional maximum powerreduction value for the serving cell c. ΔT_(IB,c) denotes an additionaltolerance for the serving cell. ΔT_(C,c) is 1.5 dB or 0 dB. ΔT_(ProSe)may be 0.1 dB. P-MPR_(c) is an allowed maximum output power reduction.

On the basis of the maximum output power P_(CMAX,c) determined byEquation 16, the transmit power P_(PSDCH) used in the discovery signaltransmission may be determined by the following equation.P _(PSDCH)=min{P _(CMAX,PSDCH),10 log₁₀(M _(PSDCH))P_(O_PSDCH,1)+α_(PSDCH,1)·PL} [dBm]  [Equation 17]

In the above equation, P_(CMAX,PSDCH) is a value of P_(CMAX,c)determined by the UE as to an uplink subframe corresponding to asidelink subframe in which a PSDCH is transmitted. In this case, thevalue P_(CMAX,c) may be determined by the above equations 15 and 16.M_(PSDCH) is 2, and PL denotes a path loss value. P_(O_PSDCH,1) andα_(PSDCH,1) are values provided by higher layer parameters.

The UE #1 transmits a discovery signal with the determined TX powerP_(PSDCH) (S103). For example, if a UE #2 is in proximity to the UE #1,it may receive the discovery signal transmitted by the UE #1.

According to the aforementioned method, a serving cell may differentlyconfigure TX power to be used by the UE #1 to transmit the discoverysignal and TX power to be used to perform uplink transmission to theserving cell. This is because P_(EMAX,c) can be announced by using‘discMaxTxPower’ instead of the existing IE P-Max. Therefore,interference inside cell coverage can be regulated by adjusting TX powerof a UE which transmits a discovery signal inside the cell coverage.Further, since TX power for discovery signal transmission can bedetermined by considering a range class of the UE, an unnecessary powerwaste can also be avoided.

Alternatively, when an operation of transmitting a discovery signal isperformed by a UE which intends to perform a D2D operation in an SF # Nof a Cell # C, a value P_(CMAX,C)(N) (and/or P_(CMAX)(N)) to be usedwhen determining discovery signal TX power may be calculated bysubstituting a maximum (discovery) TX power value corresponding to aparameter P-Max of the Cell # C related to WAN UL communication,received via a pre-defined signal (e.g., SIB 1) to a parameterP_(EMAX,C).

That is, TX power P_(PSDCH) for D2D discovery signal transmission may bedetermined on the basis of maximum output power P_(CMAX,c) at a servingcell c or P_(CMAX). In this case, the maximum output power P_(CMAX,c) atthe serving cell c or the P_(CMAX) is determined on the basis of a powervalue P_(EMAX,C) configured by the network. The power value P_(EMAX,C)configured by the network may be determined by power informationdiscMaxTxPower for the D2D discovery signal transmission or powerinformation P-Max for D2D communication.

For another example, when a UE which exists inside cell coverage (thismay be referred to as IN-COVERAGE: “INC”) performs a signal transmissionoperation based on D2D communication on an SF # N of a specific Cell #C, a value P_(CMAX,C)(N) (and/or P_(CMAX)(N)) to be used whendetermining signal TX power based on D2D communication may be calculatedby substituting a maximum (communication) TX power value correspondingto a parameter P-Max of the Cell # C related to WAN UL communication(received via a pre-defined signal (e.g., SIB 1)) to a parameterP_(EMAX,C).

For another example, when a UE which exists outside cell coverage (thismay be referred to as OUT-OF-COVERAGE (OOC)) performs a transmissionoperation of D2D communication, a value P_(CMAX,C)(N) (and/orP_(CMAX)(N)) to be used when determining D2D communication TX power maybe calculated by substituting a maximum (communication) TX power valuecorresponding to a predetermined parameter P-Max related to a Carrier #C (received via a pre-defined signal) to a parameter P_(EMAX,C).

For another example, when a UE performs an operation of transmitting adiscovery signal on an SF # N of a specific Cell # C, a valueP_(CMAX,C)(N) (and/or P_(CMAX)(N)) to be used when determining discoverysignal TX power may be calculated by substituting a value derivedthrough a pre-defined function to a parameter P_(EMAX,C).

The function may be MIN {a maximum (communication) TX power value (usedin D2D communication) corresponding to the parameter P-Max of the Cell #C related to WAN UL communication (received via a pre-defined signal(SIB 1)), a value P_(PowerClass), a maximum (discovery) TX power value(used in discovery signal transmission) corresponding to a parameterdiscMaxTxPower-r12}. Alternatively, the function may be defined as MIN{a maximum (communication) TX power value (used in D2D communication)corresponding to the parameter P-Max of the Cell # C related to WAN ULcommunication (received via a pre-defined signal (SIB 1)), a valueP_(PowerClass)}.

For example, when an in-coverage UE performs a D2D communicationtransmission operation (or when an out-of-coverage UE performs a D2Dcommunication transmission operation) on an SF # N of a specific Cell #C, a value P_(CMAX,C)(N) (and/or P_(CMAX)(N)) to be used whendetermining D2D communication TX power may be calculated by substitutinga result value of the function (or a maximum TX power valuecorresponding to a parameter discMaxTxPower-r12 relate do the Cell # C(received via a pre-defined signal (SIB19))) to a parameter P_(EMAX,C).

The aforementioned [proposed method #1] may be limitedly applied only toa UE which is capable of both discovery and D2D communication, or a UEwhich simultaneously performs discovery signal transmission and D2Dcommunication transmission or to which both of the discovery and the D2Dcommunication are configured via higher layer signaling, or a UE whichis capable of only the discovery (a UE which performs only the discoverytransmission or to which only the discovery is configured via the higherlayer signaling), or a UE which is capable of only the D2D communication(or a UE which performs only the D2D communication transmission or towhich only the D2D communication is configured via the higher layersignaling).

[Proposed method #2] The proposed method #2 relates to a method ofdetermining TX power when transmitting a PSSS (and/or a PSBCH) inassociation with D2D discovery (hereinafter, also simply referred to asdiscovery) and/or a method of determining TX power when transmitting aPSSS (and/or a PSBCH) in association with D2D communication. On thebasis of some or all of rules described below, TX power may bedetermined when transmitting the PSSS and/or PSBCH related to the D2Ddiscovery and/or the D2D communication (or triggered (simultaneously) bythe D2D discovery and/or the D2D communication).

The following rules may be limitedly applied only to a UE which iscapable of both discovery and D2D communication, or a UE whichsimultaneously performs discovery signal transmission and D2Dcommunication transmission or to which both of the discovery and the D2Dcommunication are configured via higher layer signaling, or a UE whichis capable of only the discovery (a UE which performs only the discoverytransmission or to which only the discovery is configured via the higherlayer signaling), or a UE which is capable of only the D2D communication(or a UE which performs only the D2D communication transmission or towhich only the D2D communication is configured via the higher layersignaling).

Further, the following rules may be limitedly applied only to a UEsupporting D2D on a network (or cell) which configures (or can support)both of the discovery and the D2D communication.

Further, for example, in the following rules, TX power of a PSSS (and/orPSBCH) (related to discovery and/or D2D communication or(simultaneously) triggered by discovery and/or D2D communication)transmitted by a UE which is capable of both discovery and D2Dcommunication (or a UE which simultaneously performs discovery signaltransmission and D2D communication transmission or to which both of thediscovery and the D2D communication are configured via higher layersignaling) or a UE which is capable of only the discovery (or a UE whichperforms only the discovery transmission or to which only the discoveryis configured via the higher layer signaling), or a UE which is capableof only the D2D communication (or a UE which performs only the D2Dcommunication transmission or to which only the D2D communication isconfigured via the higher layer signaling) may calculate a valueP_(CMAX,C)(N) (and/or P_(CMAX)(N)) used when determining the TX power ofthe PSSS (and/or PSBCH) (related to discovery and/or D2D communicationor (simultaneously) triggered by discovery and/or D2D communication) bysubstituting MIN {a maximum D2D communication TX power value, a maximumdiscovery TX power value} (or MAX {a maximum D2D communication TX powervalue, a maximum discovery TX power value} or a maximum D2Dcommunication TX power value or a maximum discovery TX power value) to aparameter P_(EMAX,C) according to: 1) whether there is an SIB 19 and/oran SIB 18; and 2) whether there is ‘syncConfig’ of D2D communicationand/or ‘syncConfig’ of discovery (or whether decoding is possible).

Example #2-1

Assume that a UE which is capable of both discovery and D2Dcommunication (or a UE which simultaneously performs discovery signaltransmission and D2D communication transmission or to which both of thediscovery and the D2D communication are configured via higher layersignaling) or a UE which is capable of only the discovery (or a UE whichperforms only the discovery transmission or to which only the discoveryis configured via the higher layer signaling), or a UE which is capableof only the D2D communication (or a UE which performs only the D2Dcommunication transmission or to which only the D2D communication isconfigured via the higher layer signaling) exists inside cell coverage.The UE may calculate a value P_(CMAX,C)(N) (and/or P_(CMAX)(N)) usedwhen determining TX power of a PSSS (and/or PSBCH) (related to discoveryand/or D2D communication or (simultaneously) triggered by discoveryand/or D2D communication) by substituting MIN {a maximum D2Dcommunication TX power value, a maximum discovery TX power value} or MAX{a maximum D2D communication TX power value, a maximum discovery TXpower value} to a parameter P_(EMAX,C).

Herein, for example, a maximum D2D communication TX power value may bedefined as a maximum (D2D communication) TX power value corresponding toa parameter P-Max of a Cell # C related to WAN UL communication,received via a pre-defined signal (e.g., SIB 1).

Further, a maximum discovery TX power value may be defined as a maximum(discovery) TX power value corresponding to a parameter‘discMaxTxPower-r12’ related to a Cell # C, received via a pre-definedsignal (e.g., SIB 19).

Further, for example, a UE which is capable of both discovery and D2Dcommunication (or a UE which simultaneously performs discovery signaltransmission and D2D communication transmission or to which both of thediscovery and the D2D communication are configured via higher layersignaling) or a UE which is capable of only the discovery (or a UE whichperforms only the discovery transmission or to which only the discoveryis configured via the higher layer signaling), or a UE which is capableof only the D2D communication (or a UE which performs only the D2Dcommunication transmission or to which only the D2D communication isconfigured via the higher layer signaling), which exists inside cellcoverage, may calculate a value P_(CMAX,C)(N) (and/or P_(CMAX)(N)) usedwhen determining TX power of a PSSS (and/or PSBCH) related to discoveryand/or D2D communication (or (simultaneously) triggered by discoveryand/or D2D communication)) by substituting the (aforementioned) maximumD2D communication TX power value (or maximum discovery TX power value)to a parameter P_(EMAX,C).

Further, for example, if a UE which is capable ofsupporting(/performing) only the discovery (or a UE which performs onlythe discovery transmission or to which only the discovery is configuredfor higher layer signaling) exists inside cell coverage, the UE maycalculate a value P_(CMAX,C)(N) (and/or P_(CMAX)(N)) used whendetermining TX power of a PSSS (and/or PSBCH) related to the discoverytransmission (or triggered by the discovery) by substituting the(aforementioned) maximum D2D communication TX power value (or maximumdiscovery TX power value) to a parameter P_(EMAX,C).

Further, for example, if a UE which is capable of both discovery and D2Dcommunication (or a UE which simultaneously performs discovery signaltransmission and D2D communication transmission or to which both of thediscovery and the D2D communication are configured via higher layersignaling) or a UE which is capable of only the discovery (or a UE whichperforms only the discovery transmission or to which only the discoveryis configured via the higher layer signaling), or a UE which is capableof only the D2D communication (or a UE which performs only the D2Dcommunication transmission or to which only the D2D communication isconfigured via the higher layer signaling) exists outside cell coverage,the UE may calculate a value P_(CMAX,C)(N) (and/or P_(CMAX)(N)) usedwhen determining TX power of a PSSS (and/or PSBCH) related to D2Dcommunication transmission (or triggered by D2D communication) bysubstituting a maximum D2D communication TX power value (or a maximumdiscovery TX power value or MIM {a maximum D2D communication TX powervalue, a maximum discovery TX power value} or MAX {a maximum D2Dcommunication TX power value, a maximum discovery TX power value}) to aparameter P_(EMAX,C).

For example, (Example #2-1) may be configured to be limitedly appliedonly to a UE which is capable of both discovery and D2D communication(or which simultaneously performs discovery transmission and D2Dcommunication transmission or to which the discovery and the D2Dcommunication are configured via a higher layer signal) (or a UE whichis capable of only the discovery (or which performs only the discoverytransmission or to which only the discovery is configured via the higherlayer signal) or a UE which is capable of only the D2D communication (orwhich performs only the D2D communication or to which only the D2Dcommunication is configured via the higher layer signal)).

Further, for example, (Example #2-1) may be supported by receiving (ordecoding) an SIB 19 (and/or an SIB 18) irrespective of whether thediscovery and/or the D2D communication are possible.

Further, for example, even if the UE which is capable of both thediscovery and the D2D communication (or which simultaneously performsthe discovery transmission and the D2D communication transmission or towhich the discovery and the D2D communication are configured via thehigher layer signal) exists inside cell coverage, if only a discoveryoperation (or discovery transmission) is performed (or is configured(via the higher layer signal)), a value P_(CMAX,C)(N) (and/orP_(CMAX)(N)) used when determining TX power of a PSSS (and/or PSBCH)related to the discovery transmission (or triggered by the discovery)may be calculated by substituting a maximum discovery TX power value (ora maximum D2D communication TX power value) to a parameter P_(EMAX,C).

FIG. 11 shows a method of determining TX power for a D2D signal of a UEaccording to the aforementioned ‘Example #2-1’.

Referring to FIG. 11, with respect to a UE related to a serving cell, itis determined whether an SSS/PSBCH is triggered for D2D communication(S110).

If the SSS/PSBCH is triggered for the D2D communication (a case wherethe SSS/PSBCH is triggered for only the D2D communication and a casewhere the SSS/PSBCH is triggered for both of the D2D communication andD2D discovery may be included), TX power for the SSS/PSBCH is determinedon the basis of a TX power parameter P-Max applied to the D2Dcommunication (S111). The SSS, that is, a sidelink synchronizationsignal, may include a PSSS and/or an SSSS. TX power for the PSSS and theSSSS may be determined either equally or to be different from eachother. The TX power for the PSSS and the TX power for the PSBCH may bedetermined equally. For example, the P-Max may be provided to a UE bybeing included in an SIB 1. For example, the UE may calculateP_(CMAX,PSBCH) by using a value provided by the P-Max as P_(EMAX,c).

The UE transmits the SSS/PSBCH with the determined TX power for theSSS/PSBCH (S112).

Meanwhile, with respect to the UE related to the serving cell, if theSSS/PSBCH is not triggered for the D2D communication (this may be a casewhere the SSS/PSBCH is transmitted (only) by the D2D discovery(transmission) (or (only) for the D2D discovery (transmission)), the UEdetermines TX power for the SSS/PSBCH on the basis of a TX powerparameter discMaxTxPower applied to the D2D discovery (S113). The SSS,that is, a sidelink synchronization signal, may include a PSSS and/or anSSSS. TX power for the PSSS and the SSSS may be determined eitherequally or to be different from each other. For example, the P-Max maybe provided to a UE by being included in an SIB 1. For example, thediscMaxTxPower may be provided via an SIB 19.

The UE transmits the SSS/PSBCH with the determined TX power for theSSS/PSBCH (S114).

Each value of the TX power for the SSS (SLSS) and the PSBCH may bedetermined according to whether the SSS (SLSS) and the PSBCH aretriggered (only) for the D2D discovery (or triggered (only) by the D2Ddiscovery transmission) or are triggered for the D2D communication (forexample, a case where SSS (SLSS) and PSBCH transmission aresimultaneously triggered by the D2D communication and the D2D discoverymay be included). That is, the TX power for the SSS and the PSBCH (e.g.,P_(PSSS), P_(PSBCH)) may be determined on the basis of maximum outputpower P_(CMAX,c) at a serving cell c or P_(CMAX). In this case, themaximum output power P_(CMAX,c) at the serving cell c or the P_(CMAX) isdetermined on the basis of a power value P_(EMAX,C) configured by thenetwork. The power value P_(EMAX,C) configured by the network may bedetermined by power information discMaxTxPower for the D2D discoverysignal transmission or power information P-Max for D2D communication.

As described above, the SSS/PSBCH may be triggered for the D2D discovery(or by the D2D discovery (transmission), or may be triggered for the D2Dcommunication (or by the D2D communication (transmission)). However, ifit is triggered (or simultaneously by D2D discovery (transmission) andD2D communication (transmission)) for both of the D2D discovery and theD2D communication on the same subframe (previously configured(/signaled) for an SSS/PSCBH transmission usage), how to determine TXpower for the SSS/PSBCH transmission may be a matter to be considered.

FIG. 12 shows an example of a method of determining TX power when anSSS/PSBCH is triggered for both of D2D discovery and D2D communication(or simultaneously by D2D discovery (transmission) and D2D communication(transmission) on the same subframe.

Referring to FIG. 12, on a 1st subframe 121, an SSS/PSBCH triggered for(only) the D2D discovery (or by (only) D2D discovery (transmission)) istransmitted. In this case, the SSS/PSBCH is transmitted with TX powerdetermined on the basis of discMaxTxPower. In a 2nd subframe 122, anSSS/PSBCH triggered for (only) the D2D communication (or by (only) theD2D communication (transmission)) is transmitted. In this case, theSSS/PSBCH is transmitted with TX power determined on the basis of P-Max.

However, on a specific subframe 123 (previously configured (/signaled)for an SSS/PSBCH transmission usage), the SSS/PSBCH may be triggered forboth of the D2D discovery and the D2D communication (or simultaneouslyby the D2D discovery (transmission) and the D2D communication(transmission)). In this case, the SSS/PSBCH is transmitted with the TXpower determined on the basis of the P-Max. That is, a final TX powervalue is derived on the basis of the P-Max used in determining ofSSS/PSBCH TX power (see 122) for (only) the D2D communication (or by(only) the D2D communication (transmission)). Although such a conclusionis also derived by FIG. 11, it is more clearly shown in FIG. 12. In FIG.12, a mutual time relation of each of the subframes 121, 122, and 123 isfor exemplary purposes only.

Example #2-2

when a UE performs a discovery transmission operation on an SF # N of aspecific Cell # C, a TX power value derived according to some or all ofequations among the following equations 18 to 25 may be applied to PSSS(and/or PSBCH) transmission of the discovery operation.

Herein, a value P_(CMAX,C)(N) (and/or P_(CMAX)(N)) related to PSSS(and/or PSBCH) transmission of the discovery operation, which iscalculated by substituting a maximum (communication) TX power valuecorresponding to a parameter P-Max of a Cell # C related to WAN ULcommunication, received via a pre-defined signal (SIB 1), to a parameterP_(EMAX,C), is called “PCMAXC_DIS” and “PCMAX_DIS”, respectively.

Further, a maximum (discovery) TX power value corresponding to aparameter discMaxTxPower-r12 related to a Cell # C, received via apre-defined signal (SIB 19), is named as “MAX_DIS”.

Further, (Example #2-2) may be configured to be limitedly applied onlyto a UE which is capable of both discovery and D2D communication (orwhich simultaneously performs discovery transmission and D2Dcommunication transmission or to which the discovery and the D2Dcommunication are configured via a higher layer signal) (or a UE whichis capable of only the discovery (or which performs only the discoverytransmission or to which only the discovery is configured via the higherlayer signal) or a UE which is capable of only the D2D communication (orwhich performs only the D2D communication or to which only the D2Dcommunication is configured via the higher layer signal)).MIN{MAX_DIS,MIN{PCMAXC_DIS,(10 log(M _(PSSS))+P _(O_PSSS)+α_(PSSS)·PL)}}[dBm]  [Equation 18]MIN{MAX_DIS,PCMAX_DIS,MIN{PCMAXC_DIS,(10 log(M _(PSSS))+P_(O_PSSS)+α_(PSSS)·PL)}} [dBm]  [Equation 19]MAX{MAX_DIS,MIN{PCMAXC_DIS,(10 log(M _(PSSS))+P_(O_PSSS)+α_(PSSS)·PL)}}[dBm]  [Equation 20]MAX{MAX_DIS,PCMAX_DIS,MIN{PCMAXC_DIS,(10 log(M _(PSSS))+P_(O_PSSS)+α_(PSSS)·PL)}} [dBm]  [Equation 21]MIN{PCMAX_DIS,MIN{MAX_DIS,PCMAXC_DIS,(10 log(M _(PSSS))+P_(O_PSSS)+α_(PSSS)·PL)}} [dBm]  [Equation 22]MIN {PCMAX_DIS,MIN {MAX_DIS,(10 log(M _(PSSS))+P_(O_PSSS)+α_(PSSS)·PL)}}[dBm]  [Equation 23]MAX{PCMAX_DIS,MIN{MAX_DIS,PCMAXC_DIS,(10 log(M _(PSSS))+P_(O_PSSS)+α_(PSSS)·PL)}} [dBm]  [Equation 24]MAX{PCMAX_DIS,MIN{MAX_DIS,(10 log(M _(PSSS))+P_(O_PSSS)+α_(PSSS)·PL)}}[dBm]  [Equation 25]

[Proposed method #3] A parameter P_(CMAX,C)(N) (and/or P_(CMAX)(N)) usedin determining of TX power of a D2D signal transmitted on an SF # N of aspecific Cell # C may be calculated by assuming a case where apre-defined (or signaled) WAN UL signal is transmitted (equally)according to an allocated-resource count/position and/or modulationrelated to D2D signal transmission.

Herein, for example, the WAN UL signal may be configured through aPUSCH. Applying of this method can also be interpreted such that MPR_(c)(or MPR) and/or A-MPR_(c) (or A-MPR) related to D2D signal transmissionare (additionally) defined.

Further, for example, [Proposed method #3] may be applied limitedly onlywhen a single UL cell is configured and/or when multiple UL cells areconfigured with carrier aggregation (CA) and WAN UL transmission doesnot exist on another cell (partially or entirely) overlapping with an SF# N for transmitting a D2D signal of a Cell # C.

[Proposed method #4] A rule may be defined such that a parameterP_(CMAX)(N) (and/or P_(CMAX,C)(N)) used in determining of TX power for aWAN UL signal transmitted on an SF # N of a specific Cell # C iscalculated under the assumption that there is no D2D signal transmissionin (some or all of) subframes on another cell overlapping with the SF #N.

Specifically, for example, in case of applying the rule to theaforementioned ‘CASE (1)’, even if D2D signal transmission and WAN ULsignal transmission must be performed (or scheduled) respectively in anSF # Q of a Cell # A and an SF # P of a Cell # B, a parameterP_(CMAX)(P) (and/or P_(CMAX,B)(P)) used in determining of TX power ofthe WAN UL signal transmitted on the SF # P of the Cell # B may becalculated under the assumption that there is no D2D signal transmissionin the SF # Q of the Cell # A.

For another example, in case of applying the rule to the aforementioned‘CASE (2)’, even if D2D signal transmission, WAN UL signal transmission,and WAN UL signal transmission must be performed (or scheduled)respectively in an SF # Q of a Cell # A, an SN # P of a Cell # B, and anSB #(P+1) of the Cell # B, a parameter P_(CMAX)(P) (and/orP_(CMAX,B)(P)) and a parameter P_(CMAX)(P+1) (and/or P_(CMAX,B)(P+1))may be calculated under the assumption that there is no D2D signaltransmission in the SF # Q of the Cell # A.

By applying this method, TX power of a D2D signal does not have aneffect on determining of TX power of a WAN UL signal.

For another example, if there is D2D signal transmission in a subframeon another cell partially or entirely overlapping with the SF # N, aparameter P_(CMAX)(N) (and/or P_(CMAX,C)(N)) used in determining of TXpower of a WAN UL signal transmitted in an SF # N of a specific Cell # Cmay be calculated under the assumption that a pre-defined (or signaled)WAN UL signal is transmitted (together) (in addition to WAN UL signaltransmission in the SF # N of the Cell # C) according to anallocated-resource count/position and/or modulation related to D2Dsignal transmission.

Herein, when a D2D signal is transmitted in a subframe on another Cell #X (partially or entirely) overlapping with the SF # C of the Cell # Cfor transmitting a WAN UL signal, a parameter P_(CMAX)(N) (and/orP_(CMAX,X)(N)) used in determining of TX power for the D2D signal may becalculated under the assumption that a pre-defined (or signaled) WAN ULsignal is transmitted (together) (in a Cell # X) in addition to WAN ULsignal transmission in the SF # N of the Cell # C according to anallocated-resource count/position and/or modulation related to D2Dsignal transmission.

Specifically, for example, in case of applying the rule to ‘CASE (1)’,if D2D signal transmission and WAN UL signal transmission must beperformed (or scheduled) respectively in the SF # Q of the Cell # A andthe SF # P of the Cell # B, a parameter P_(CMAX)(P) (and/orP_(CMAX,B)(P)) used in determining of TX power of a WAN UL signal on theSF # P of the Cell # B may be calculated under the assumption that apre-defined (or signaled) WAN UL signal is transmitted (together) in theSF # Q of the Cell # A (in addition to WAN UL signal transmission in theSF # N of the Cell # C) according to an allocated-resourcecount/position/modulation related to D2D signal transmission.

When applying this method, TX power of the D2D signal has an effect ondetermining of TX power of the WAN UL signal.

Further, for example, [Proposed method #4] may be limitedly applied onlyto intra-band contiguous carrier aggregation (contiguous resourceallocation and/or non-contiguous resource allocation may be used) and/orintra-band non-contiguous carrier aggregation (two UL carriers may beused).

[Proposed method #5] TX power of a D2D signal transmitted in an SF # Nof a specific Cell # C may be calculated according to some or all ofrules described below.

A rule may be defined such that D2D_TXP(Q) and/or D2D_TXP(Q+1) derivedthrough the following rules are finally determined through an operationof MIN {D2D_TXP(Q), a maximum (discovery) TX power value correspondingto a parameter discMaxTxPower-r12} (or MAX {D2D_TXP(Q), a maximum(discovery) TX power value corresponding to a parameterdiscMaxTxPower-r12}) and/or MIN {D2D_TXP(Q+1), a maximum (discovery) TXpower value corresponding to a parameter discMaxTxPower-r12}(or MAX{D2D_TXP(Q+1), a maximum (discovery) TX power value corresponding to aparameter discMaxTxPower-r12}).

Example #5-1

For ‘CASE (1)’, for example, if D2D signal transmission and WAN ULsignal transmission must be (simultaneously) performed respectively onthe SF # Q of the Cell # A and the SF # P of the Cell # B, TX power of aD2D signal in the SF # Q of the Cell # A may be determined according tothe following rule.

1) At a (partially or entirely) overlapping time (subframe) on othercells, the TX power of the D2D signal in the SF # Q of the Cell # A maybe determined on the basis of P_(CMAX)(P) (“PCMAX_WO(P)”) (orP_(CMAX_L)(P) (“PCMAXL_WO(P)”)) or P_(CMAX,B)(P) related to WAN ULsignal transmission (in the SF # P of the Cell # B) calculated under theassumption that there is no D2D signal transmission.

If it is assumed that WAN UL signal TX power in the SF # P of the Cell #B determined by an open-loop/closed-loop power control (OLPC/CLPC)parameter is denoted by “WAN_CONP(P)”, final WAN UL signal TX power at acorresponding time (this is called “WAN_TXP(P)”) may be determined asMIN {PCMAX_WO(P), MIN {P_(CMAX,B)(P), WAN_CONP(P)}}.

2) Under the assumption that a pre-defined (or signaled) WAN UL signalis transmitted together according to an allocated-resourcecount/position/modulation related to D2D signal transmission in additionto WAN UL signal transmission in the SF # P of the Cell # B, the TXpower of the D2D signal in the SF # Q of the Cell # A may be determinedon the basis of the calculated P_(CMAX)(Q(/P)) (this is called“PCMAX_DW(Q(/P))”) (or P_(CMAX_L)(Q(/P)) (“PCMAXL_DW(Q(/P))”)) orP_(CMAX,A)(Q(/P)) related to D2D signal transmission (in the SF # Q ofthe Cell # A).

Herein, in this rule, WAN UL signal transmission (in the SF # P of theCell # B) may be interpreted as a reference for calculating D2D signalTX power (in the SF # Q of the Cell # A) (e.g., PCMAX_DW(P(/Q)) (orPCMAXL_DW(P(/Q)))).

For example, if TX power of a D2D signal at the SF # Q of the Cell # A,which is determined by an open-loop power control (OLPC) parameter, isassumed as “D2D_CONP(Q)”, TX power of a final D2D signal at acorresponding time (this is denoted by “D2D_TXP(Q)”) may be determinedas MIN {(PCMAX_DW(Q(/P))−WAN_TXP(P)), MIN {PCMAX,A(Q), D2D_CONP(Q)}}. Ifthis method is applied, it may be interpreted that WAN_TXP(P) is notinfluenced by D2D_TXP(Q). Further, for example, in the above equation,PCMAX_DW(Q(/P)) may be replaced with P_(PowerClass) or MIN {P_(EMAX,A),P_(PowerClass)}.

For example, if D2D_TXP(Q) cannot satisfy an emission requirementpre-defined (or signaled) in a simultaneous transmission situation of aWAN UL signal/D2D signal, a rule may be defined such that D2D_TXP(Q) ispreferentially decreased until the emission requirement is satisfied.

For another example, in order to solve such a problem, a rule may bedefined such that a pre-defined (or signaled) power offset value isadditionally applied to (final) D2D_TXT(Q). For another example, ifD2D_TXP(Q) cannot satisfy the pre-defined (or signaled) emissionrequirement in the simultaneous transmission situation of the WAN ULsignal/D2D signal, a rule may be defined such that transmission of theD2D signal is omitted.

Example #5-2

For ‘CASE (1)’, for example, if D2D signal transmission is performed inan SF # Q of a Cell # A and WAN UL signal transmission is not performedin an SF # P of a Cell # B, a rule may be defined such that TX power ofa D2D signal in the SF # Q of the Cell # A is determined according tothe following rule.

1) Under the assumption that a pre-defined (or signaled) WAN UL signalis transmitted according to an allocated-resourcecount/position/modulation related to D2D signal transmission, TX powerof a D2D signal in the SF # Q of the Cell # A may be determined on thebasis of P_(CMAX)(Q) (“PCMAX_OD(Q)”) (or P_(CMAX_L)(Q) (“PCMAXL_OD(Q)”))or P_(CMAX,A)(Q) related to D2D signal transmission (in the SF # Q ofthe Cell # A).

For example, if TX power of a D2D signal at the SF # Q of the Cell # A,which is determined by an open-loop power control (OLPC) parameter, isassumed as “D2D_CONP(Q)”, TX power of a final D2D signal at acorresponding time (this is denoted by “D2D_TXP(Q)”) may be determinedas MIN {PCMAX_OD(Q), MIN {P_(CMAX,A)(Q), D2D_CONP(Q)}}.

Further, for example, in the above equation, PCMAX_OD(Q) related todetermining of D2D_TXP(Q) may be replaced with P_(PowerClass) or MIN{P_(EMAX,A), P_(PowerClass)}.

Example #5-3

For ‘CASE (1)’, if D2D signal transmission and WAN UL signaltransmission must be (simultaneously) performed respectively on the SF #Q of the Cell # A and the SF # P of the Cell # B, the TX power of theD2D signal in the SF # Q of the Cell # A may be determined according tothe following rule.

Under the assumption that a pre-defined (or signaled) WAN UL signal istransmitted together in addition to WAN UL signal transmission in the SF# P of the Cell # B according to an allocated-resourcecount/position/modulation related to D2D signal transmission, the TXpower of the D2D signal in the SF # Q of the Cell # A may be determinedon the basis of calculated P_(CMAX,A)(Q) related to D2D signaltransmission (in the SF # Q of the Cell # A), P_(CMAX,B)(P) related toWAN UL signal transmission (in the SF # P of the Cell # B) andP_(CMAX)(Q(/P)) related to D2D signal transmission/WAN UL signaltransmission (“PCMAX_DW(Q(/P))”) (or P_(CMAX_L)(Q(/P))(“PCMAXL_DW(Q(/P))”)).

Herein, for example, according to such a rule, WAN UL signaltransmission (in the SF # P of the Cell # B) may be interpreted as areference for calculating D2D signal TX power (in the SB # Q of the Cell# A) (e.g., e.g., PCMAX_DW(P(/Q)) (or PCMAXL_DW(P(/Q)))).

For example, if TX power of a D2D signal in the SF # Q of the Cell # Adetermined by an open-loop power control (OLPC) parameter is assumed as“D2D_CONP(Q)” and if TX power of a WAN UL signal in the SF # P of theCell # B determined by an open-loop power control (OLPC)/closed-looppower control (CLPC) parameter is assumed as “WAN_CONP(P)”, TX power ofa final WAN UL signal in the SF # P of the Cell # B (“WAN_TXP(P)”) maybe determined as MIN {PCMAX_DW(P(/Q)), MIN {P_(CMAX,B)(P),WAN_CONP(P)}}, and TX power of a final D2D signal in the SF # Q of theCell # A (“D2D_TXP(Q)”) may be determined as MIN{(PCMAX_DW(Q(/P))−WAN_TXP(P)), MIN {P_(CMAX,A)(Q), D2D_CONP(Q)}}.

If this method is applied, it may be interpreted that WAN_TXP(P) isinfluenced by D2D_TXP(Q). Further, for example, in the above equation,PCMAX_DW(Q(/P)) may be replaced with P_(PowerClass) or MIN {P_(EMAX,A),P_(PowerClass)}.

For example, if D2D_TXP(Q) cannot satisfy the pre-defined (or signaled)emission requirement in the simultaneous transmission situation of theWAN UL signal/D2D signal, D2D_TXP(Q) may be preferentially decreaseduntil the emission requirement is satisfied. For another example, inorder to solve such a problem, a pre-defined (or signaled) power offsetvalue may be additionally applied to (final) D2D_TXT(Q). For anotherexample, if D2D_TXP(Q) cannot satisfy the pre-defined (or signaled)emission requirement in the simultaneous transmission situation of theWAN UL signal/D2D signal, a rule may be defined such that transmissionof the D2D signal is omitted.

Example #5-4

For CASE (1), for example, if D2D signal transmission and WAN UL signaltransmission must be (simultaneously) performed respectively on the SF #Q of the Cell # A and the SF # P of the Cell # B, the TX power of theD2D signal in the SF # Q of the Cell # A may be determined according tothe following rule.

At a (partially or entirely) overlapping subframe (time) on othercell(s), the TX power of the D2D signal in the SF # Q of the Cell # Amay be determined on the basis of P_(CMAX)(P) (“PCMAX_WO(P)”) (orP_(CMAX_L)(P) (“PCMAXL_WO(P)”)) or P_(CMAX,B)(P) related to WAN ULsignal transmission (in the SF # P of the Cell # B) calculated under theassumption that there is no D2D signal transmission.

For example, if TX power of a WAN UL signal in an SF # P of the Cell # Bdetermined by an open-loop power control/closed-loop power controlparameter is assumed as “WAN_CONP(P)”, TX power of a final WAN UL signalat a corresponding time(“WAN_TXP(P)”) may be determined as MIN{PCMAX_WO(P), MIN {P_(CMAX,B)(P), WAN_CONP(P) }}.

Under the assumption that a pre-defined (or signaled) WAN UL signal istransmitted together in addition to WAN UL signal transmission in the SF# P of the Cell # B according to an allocated-resourcecount/position/modulation related to D2D signal transmission, TX powerof a D2D signal in the SF # Q of the Cell # A may be determined on thebasis of P_(CMAX)(Q(/P)) (“PCMAX_DW(Q(/P))”) (or P_(CMAX_L)(Q(/P))(“PCMAXL_DW(Q(/P))”)) or PP_(CMAX,A)(Q(/P)) related to calculated D2Dsignal transmission (in the SF # Q of the Cell # A).

In this rule, WAN UL signal transmission (in the SF # P of the Cell # B)may be interpreted as a reference for calculating D2D signal TX power(in the SF # Q of the Cell # A) (e.g., PCMAX_DW(P(/Q)) (orPCMAXL_DW(P(/Q)))).

If TX power of a D2D signal in the SF # Q of the Cell # A determined byan open-loop power control parameter is assumed as “D2D_CONP(Q)”, TXpower of a final D2D signal at a corresponding time(“D2D_TXP(Q)”) may bedetermined as MIN {(NEW_VAL−WAN_TXP(P)), MIN {P_(CMAX,A)(Q),D2D_CONP(Q)}}. Herein, for example, NEW_VAL may be determined as MIN{PCMAXL_WO(P), PCMAXL_DW(Q(/P))} (or MAX {PCMAXL_WO(P),PCMAXL_DW(Q(/P))} or MIN {PCMAX_WO(P), PCMAX_DW(Q(/P))} or MAX{PCMAX_WO(P), PCMAX_DW(Q(/P))} or PCMAXL_WO(P) or PCMAXL_DW(Q(/P))).Further, for example, NEW_VAL related to determining of D2D_TXP(Q) maybe replaced with P_(PowerClass) or MIN {P_(EMAX,A), P_(PowerClass)}.

For example, if D2D_TXP(Q) cannot satisfy an emission requirementpre-defined (or signaled) in a simultaneous transmission situation of aWAN UL signal/D2D signal, a rule may be defined such that D2D_TXP(Q) ispreferentially decreased until the emission requirement is satisfied.For another example, in order to solve such a problem, a rule may bedefined such that a pre-defined (or signaled) power offset value isadditionally applied to (final) D2D_TXT(Q). For another example, ifD2D_TXP(Q) cannot satisfy the pre-defined (or signaled) emissionrequirement in the simultaneous transmission situation of the WAN ULsignal/D2D signal, a rule may be defined such that transmission of theD2D signal is omitted.

FIG. 13 is an example of CASE (2).

Referring to FIG. 13, an SF # Q of a Cell # A and an SF # P of a Cell #B are not time-synchronized, and the SF # Q of the Cell # A fortransmitting a D2D signal partially overlaps with SFs # P and (P+1) of aCell # B for transmitting a WAN UL signal.

Example #5-5

Under the premise of the aforementioned ‘CASE (2)’ or a modified exampleof ‘CASE (2)’ of FIG. 13, if D2D signal transmission, WAN UL signaltransmission, WAN UL signal transmission, and WAN UL signal transmissionmust be (simultaneously) performed respectively on the SF # Q of theCell # A, the SF # P of the Cell # B, and the SF #(P+1) of the Cell # B,TX power of a D2D signal in the SF # Q of the Cell # A may be determinedaccording to the following rule.

Herein, for example, (Example #5-5) may be interpreted as a case where aWAN UL cell (carrier) leads a D2D cell (carrier). Further, for example,in FIG. 13, a SF index ‘Q’ of the Cell # A may be assumed as an index‘K’, and an SF index ‘P (/(P+1))’ of the Cell # B may be assumed as ‘K(/(K+1))’.

At a (partially or entirely) overlapping time(s) on other cells, the TXpower of the D2D signal in the SF # Q of the Cell # A may be determinedon the basis of P_(CMAX)(P) (“PCMAX_WO(P)”) (or P_(CMAX_L)(P)(“PCMAXL_WO(P)”)) or P_(CMAX,B)(P) related to WAN UL signal transmissionin the SF # P of the Cell # B and P_(CMAX)(P+1) (“PCMAX_WO(P+1)”) (orP_(CMAX_L)(P+1) (“PCMAXL_WO(P+1)”)) or P_(CMAX,B)(P+1) related to WAN ULsignal transmission in the SF #(P+1) of the Cell # B, calculated underthe assumption that there is no D2D signal transmission.

For example, if TX power of a WAN UL signal in an SF # P of the Cell # Bdetermined by an open-loop/closed-loop power control parameter isassumed as “WAN_CONP(P)” and if TX power of a WAN UL signal in an SF#(P+1) of the Cell # B is assumed as “WAN_CONP(P+1)”, TX power of afinal WAN UL signal (“WAN_TXP(P)”) in the SF # P of the Cell # B may bedetermined as MIN {PCMAX_WO(P), MIN {P_(CMAX,B)(P), WAN_CONP(P)}}, andTX power of a final WAN UL signal in an SF #(P+1) of the Cell # B(“WAN_TXP(P+1)”) may be determined as MIN {PCMAX_WO(P+1), MIN{P_(CMAX,B)(P+1), WAN_CONP(P+1)}}.

Under the assumption that WAN UL signal transmission in the SF # P ofthe Cell # B partially overlaps with a pre-defined (or signaled) WAN ULsignal transmitted in the SF # Q of the Cell # A according to anallocated-resource count/position/modulation related to D2D signaltransmission, TX power for a D2D signal in the SF # Q of the Cell # Amay be determined on the basis of calculated P_(CMAX)(P, Q) related toD2D signal transmission (in the SF # Q of the Cell # A) (“PCMAX_DW(P,Q)”) (or P_(CMAX_L)(P, Q) (“PCMAXL_DW(P, Q)”)) or P_(CMAX,A)(P, Q).

Herein, for example, in this rule, WAN UL signal transmission (in the SF# P of the Cell # B) may be interpreted as a reference for calculatingD2D signal TX power (in the SF # Q of the Cell # A) (e.g., PCMAX_DW(Q,(P+1)) (or PCMAXL_DW(Q, (P+1)))).

Under the assumption that WAN UL signal transmission in the SF #(P+1) ofthe Cell # B partially overlaps with a pre-defined (or signaled) WAN ULsignal transmitted in the SF # Q of the Cell # A according to anallocated-resource count/position/modulation related to D2D signaltransmission, TX power for a D2D signal in the SF # Q of the Cell # Amay be determined on the basis of calculated P_(CMAX)(Q, (P+1)) relatedto D2D signal transmission (in the SF # Q of the Cell # A) (“PCMAX_DW(Q,(P+1))”) (or P_(CMAX_L)(Q, (P+1)) (“PCMAXL_DW(Q, (P+1))”)) orP_(CMAX,A)(Q, (P+1)).

Herein, for example, in this rule, WAN UL signal transmission (in the SF#(P+1) of the Cell # B) may be interpreted as a reference forcalculating D2D signal TX power (in the SF # Q of the Cell # A) (e.g.,PCMAX_DW(Q, (P+1)) (or PCMAXL_DW(Q, (P+1)))).

For example, P_(CMAX,A)(P, Q) and P_(CMAX,A)(Q, (P+1)) may have the samevalue.

For example, if TX power of a D2D signal at the SF # Q of the Cell # A,which is determined by an open-loop power control parameter, is assumedas “D2D_CONP(Q)”, TX power of a final D2D signal (“D2D_TXP(Q)”) at acorresponding time may be determined as MIN {(NEW_VAL−MAX_WANVAL), MIN{P_(CMAX,A)(Q, Q), D2D_CONP(Q)}}.

Herein, for example, NEW_VAL may be determined as MIN {PCMAXL_DW(P, Q),PCMAXL_DW(Q, (P+1))} (or MAX {PCMAXL_DW(P, Q), PCMAXL_DW(Q, (P+1))} orMIN {PCMAX_DW(P, Q), PCMAX_DW(Q, (P+1))} or MAX {PCMAX_DW(P, Q),PCMAX_DW(Q, (P+1))} or PCMAXL_DW(P, Q) or PCMAXL_DW(Q, (P+1)) orPCMAX_DW(P, Q) or PCMAX_DW(Q, (P+1))).

Further, for example, MAX_WANVAL may be determined as MAX {WAN_TXP(P),WAN_TXP(P+1)}. Furthermore, for example, NEW_VAL related to determiningof D2D_TXP(Q) may be replaced with P_(PowerClass) or MIN {P_(EMAX,A),P_(PowerClass)}.

For example, if D2D_TXP(Q) cannot satisfy an emission requirementpre-defined (or signaled) in a simultaneous transmission situation of aWAN UL signal/D2D signal, a rule may be defined such that D2D_TXP(Q) ispreferentially decreased until the emission requirement is satisfied.

For another example, in order to solve such a problem, a rule may bedefined such that a pre-defined (or signaled) power offset value isadditionally applied to (final) D2D_TXT(Q).

For another example, if D2D_TXP(Q) cannot satisfy the pre-defined (orsignaled) emission requirement in the simultaneous transmissionsituation of the WAN UL signal/D2D signal, a rule may be defined suchthat transmission of the D2D signal is omitted.

FIG. 14 is another modified example of ‘CASE (2)’.

Referring to FIG. 14, an SF # Q of a Cell # A and an SF # P of a Cell #B are not time-synchronized, and the SF # Q of the Cell # A fortransmitting a D2D signal partially overlaps with the SF # P of the Cell# B.

Example #5-6

For the aforementioned ‘CASE (2)’ or a modified example for CASE (2)exemplified in FIG. 14, for example, if D2D signal transmission and WANUL signal transmission must be (simultaneously) performed respectivelyon the SF # Q of the Cell # A and the SF # P of the Cell # B, TX powerfor a D2D signal in the SF # Q of the Cell # A may be determinedaccording to the following rule.

Herein, for example, (Example #5-6) may be interpreted as a case where aD2D cell (carrier) leads a WAN UL cell (carrier) (or a case where theWAN UL cell (carrier) leads the D2D cell (carrier)). Further, forexample, in FIG. 14, a SF index ‘Q’ of the Cell # A may be assumed as anindex ‘K’, and an SF index ‘P’ of the Cell # B may be assumed as ‘(K+1)(or ‘K’)’.

At a (partially or entirely) overlapping time (subframe) on other cells,the TX power of the D2D signal in the SF # Q of the Cell # A may bedetermined on the basis of P_(CMAX)(P) (“PCMAX_WO(P)”) (or P_(CMAX_L)(P)(“PCMAXL_WO(P)”)) or P_(CMAX,B)(P) related to WAN UL signal transmissionin the SF # P of the Cell # B, calculated under the assumption thatthere is no D2D signal transmission.

For example, if TX power of a WAN UL signal in an SF # P of the Cell # Bdetermined by an open-loop power control/closed-loop power controlparameter is assumed as “WAN_CONP(P)”, TX power of a final WAN UL signal(“WAN_TXP(P)”) in the SF # P of the Cell # B may be determined as MIN{PCMAX_WO(P), MIN {P_(CMAX,B)(P), WAN_CONP(P)}}.

Under the assumption that WAN UL signal transmission in the SF # P ofthe Cell # B partially overlaps with a pre-defined (or signaled) WAN ULsignal transmitted in the SF # Q of the Cell # A according to anallocated-resource count/position/modulation related to D2D signaltransmission, TX power for a D2D signal in the SF # Q of the Cell # Amay be determined on the basis of calculated P_(CMAX)(P, Q) related toD2D signal transmission (in the SF # Q of the Cell # A) (“PCMAX_DW(P,Q)”) (or P_(CMAX_L)(P, Q) (“PCMAXL_DW(P, Q)”)) or P_(CMAX,A)(P, Q).

Herein, for example, in this rule, WAN UL signal transmission (in the SF# P of the Cell # B) may be interpreted as a reference for calculatingD2D signal TX power (in the SF # Q of the Cell # A) (e.g., PCMAX_DW(Q,P) (or PCMAXL_DW(Q, P))).

For example, if TX power of a D2D signal at the SF # Q of the Cell # A,which is determined by an open-loop power control parameter, is assumedas “D2D_CONP(Q)”, TX power of a final D2D signal (“D2D_TXP(Q)”) at acorresponding time may be determined as MIN {(NEW_VAL−MAX_WANVAL), MIN{P_(CMAX,A)(Q, P), D2D_CONP(Q)}}.

Herein, for example, NEW_VAL may be determined as MIN {PCMAXL_WO(P),PCMAXL_DW(Q, P)} (or MAX {PCMAXL_WO(P), PCMAXL_DW(Q, P)} or MIN{PCMAX_WO(P), PCMAX_DW(Q, P)} or MAX {PCMAX_WO(P), PCMAX_DW(Q, P)} orPCMAXL_WO(P) or PCMAXL_DW(Q, P) or PCMAX_WO(P) or PCMAX_DW(Q, P)).

Further, for example, MAX_WANVAL may be determined as WAN_TXP(P).Furthermore, for example, in the above equation, NEW_VAL related todetermining of D2D_TXP(Q) may be replaced with P_(PowerClass) or MIN{P_(EMAX,A), P_(PowerClass)}.

For example, if D2D_TXP(Q) cannot satisfy an emission requirementpre-defined (or signaled) in a simultaneous transmission situation of aWAN UL signal/D2D signal, a rule may be defined such that D2D_TXP(Q) ispreferentially decreased until the emission requirement is satisfied.For another example, in order to solve such a problem, a rule may bedefined such that a pre-defined (or signaled) power offset value isadditionally applied to (final) D2D_TXT(Q). For another example, ifD2D_TXP(Q) cannot satisfy the pre-defined (or signaled) emissionrequirement in the simultaneous transmission situation of the WAN ULsignal/D2D signal, a rule may be defined such that transmission of theD2D signal is omitted.

FIG. 15 shows a power control method according to an embodiment of thepresent invention.

Referring to FIG. 15, a UE determines TX power to be applied to a 1^(st)SF of a 1^(st) cell (1st carrier) and a 2^(nd) SF of a 2^(nd) cell(2^(nd) carrier) (S151).

The UE performs WAN transmission in the 1^(st) SF of the 1^(st) cell(S152), and performs transmission based on a D2D operation in the 2^(nd)SF of the 2^(nd) cell (S153).

In this case, if the 1^(st) SF and the 2^(nd) SF partially overlaptemporally, TX power for the WAN transmission at the 1^(st) SF andtransmission based on the D2D operation at the 2^(nd) SF may bedetermined on the basis of maximum output power P_(CMAX) determined forthe 1^(st) SF of the 1^(st) cell. That is, a WAN UL cell (or a subframefor transmitting a WAN UL signal) may be a reference for calculatingP_(CMAX) (and/or P_(CMAX_L) and/or P_(CMAX_H)) related to transmissionbased on a D2D operation (performed in another cell (carrier)) and theWAN UL transmission.

In the above method, the 1^(st) SF may temporally lead the 2^(nd) SF asshown in FIG. 13, or the 1^(st) SF may temporally lag the 2^(nd) SF. The1^(st) cell and the 2^(nd) cell may be cells of different frequencies.The 1^(st) and 2^(nd) cells may be expressed respectively as 1^(st) and2^(nd) carriers.

FIG. 16 shows again the sub-figure (b) of FIG. 9 for convenience.

Referring to FIG. 16, an SF # Q and SF # Q+1 of a Cell # A and an SF # Pand SF # P+1 of a Cell # B are not aligned temporally. The SF # Q of theCell # A partially overlaps with the SF # P+1 of the Cell # B, and theSFs of the Cell # B temporally lead the SFs of the Cell # A. FIG. 16shows ‘CASE (2)’

Example #5-7

For ‘CASE (2)’ of FIG. 16, for example, if D2D signal transmission, D2Dsignal transmission, WAN UL signal transmission, and WAN UL signaltransmission must be (simultaneously) performed respectively on the SF #Q of the Cell # A, the SF #(Q+1) of the Cell # A, the SF # P of the Cell# B, and the SF #(P+1) of the Cell # B, a rule may be defined such thatTx power of a D2D signal in the SF # Q of the Cell # A and TX power of aD2D signal in the SF #(Q+1) of the Cell # A are determined according tothe following rule.

Herein, for example, (Example #5-7) may be interpreted as a case where aWAN UL cell (carrier) leads a D2D cell (carrier). Further, for example,in FIG. 16, an SF ‘Q (/(Q+1))’ of the Cell # A may be assumed as ‘K(/(K+1))’, and an SF ‘P (/(P+1))’ of the Cell # B may be assumed as ‘K(/(K+1))’.

At a (partially or entirely) overlapping time (subframe) on other cells,the TX power of the D2D signal in the SF # Q of the Cell # A and the TXpower of the D2D signal in the SF #(Q+1) of the Cell # A may bedetermined on the basis of P_(CMAX)(P) (“PCMAX_WO(P)”) (or P_(CMAX_L)(P)(“PCMAXL_WO(P)”)) or P_(CMAX,B)(P) related to WAN UL signal transmissionin the SF # P of the Cell # B and P_(CMAX)(P+1) (“PCMAX_WO(P+1)”) (orP_(CMAX_L)(P+1) (“PCMAXL_WO(P+1)”)) or P_(CMAX,B)(P+1) related to WAN ULsignal transmission in the SF #(P+1) of the Cell # B, calculated underthe assumption that there is no D2D signal transmission.

For example, if TX power of a WAN UL signal in an SF # P of the Cell # Bdetermined by an open-loop power control/closed-loop power controlparameter is assumed as “WAN_CONP(P)” and if TX power of a WAN UL signalin an SF #(P+1) of the Cell # B is assumed as “WAN_CONP(P+1)”, TX powerof a final WAN UL signal (“WAN_TXP(P)”) in the SF # P of the Cell # Bmay be determined as MIN {PCMAX_WO(P), MIN {P_(CMAX,B)(P),WAN_CONP(P)}}, and TX power of a final WAN UL signal in an SF #(P+1) ofthe Cell # B (“WAN_TXP(P+1)”) may be determined as MIN {PCMAX_WO(P+1),MIN {P_(CMAX,B)(P+1), WAN_CONP(P+1)}}.

Under the assumption that WAN UL signal transmission in the SF # P ofthe Cell # B partially overlaps with a pre-defined (or signaled) WAN ULsignal transmitted in the SF # Q of the Cell # A according to anallocated-resource count/position/modulation related to D2D signaltransmission, a rule may be defined such that TX power for a D2D signalin the SF # Q of the Cell # A and TX power of a D2D signal in the SF#(Q+1) of the Cell # A are determined on the basis of calculatedP_(CMAX)(P, Q) related to D2D signal transmission (in the SF # Q of theCell # A) (“PCMAX_DW(P, Q)”) (or P_(CMAX_L)(P, Q) (“PCMAXL_DW(P, Q)”))or P_(CMAX,A)(P, Q).

Herein, for example, in this rule, WAN UL signal transmission (in the SF# P of the Cell # B) may be interpreted as a reference for calculatingD2D signal TX power (in the SF # Q of the Cell # A) (e.g., PCMAX_DW(P,Q) (or PCMAXL_DW(P, Q))).

Under the assumption that WAN UL signal transmission in the SF #(P+1) ofthe Cell # B partially overlaps with a pre-defined (or signaled) WAN ULsignal transmitted in the SF # Q of the Cell # A (according to anallocated-resource count/position/modulation related to D2D signaltransmission), a rule may be defined such that TX power for a D2D signalin the SF # Q of the Cell # A and TX power of a D2D signal in the SF#(Q+1) of the Cell # A are determined on the basis of calculatedP_(CMAX)(Q, (P+1)) related to D2D signal transmission in the SF # Q ofthe Cell # A (“PCMAX_DW(Q, (P+1))”) (or P_(CMAX_L)(Q, (P+1))(“PCMAXL_DW(Q, (P+1))”)) or P_(CMAX,A)(Q, (P+1)).

Herein, for example, in this rule, WAN UL signal transmission (in the SF#(P+1) of the Cell # B) may be interpreted as a reference forcalculating D2D signal TX power (in the SF # Q of the Cell # A) (e.g.,PCMAX_DW(Q, (P+1)) (or PCMAXL_DW(Q, (P+1)))).

Under the assumption that WAN UL signal transmission in the SF #(P+1) ofthe Cell # B partially overlaps with a pre-defined (or signaled) WAN ULsignal transmitted in the SF #(Q+1) of the Cell # A (according to anallocated-resource count/position/modulation related to D2D signaltransmission), a rule may be defined such that TX power for a D2D signalin the SF # Q of the Cell # A and TX power of a D2D signal in the SF#(Q+1) of the Cell # A are determined on the basis of calculatedP_(CMAX)((P+1), (Q+1)) related to D2D signal transmission in the SF#(Q+1) of the Cell # A (“PCMAX_DW((P+1), (Q+1))”) (or P_(CMAX_L)((P+1),(Q+1)) (“PCMAXL_DW((P+1), (Q+1))”)) or P_(CMAX,A)((P+1), (Q+1)). Herein,for example, in this rule, WAN UL signal transmission (in the SF #(P+1)of the Cell # B) may be interpreted as a reference for calculating D2Dsignal TX power (in the SF #(Q+1) of the Cell # A) (e.g.,PCMAX_DW((P+1), (Q+1)) (or PCMAXL_DW((P+1), (Q+1)))).

For example, P_(CMAX,A)(P, Q) and P_(CMAX,A)(Q, (P+1)) may have the samevalue.

For example, if TX power of a D2D signal at an SF # Q of a Cell # A,which is determined by an open-loop power control parameter, is assumedas “D2D_CONP(Q)”, TX power of a final D2D signal at a correspondingtime(“D2D_TXP(Q)”) may be determined as MIN {(NEW_VAL−MAX_WANVAL), MIN{PCMAX,A(Q, Q), D2D_CONP(Q)}}. Herein, for example, NEW_VAL may bedetermined as MIN {PCMAXL_DW(P, Q), PCMAXL_DW(Q, (P+1))} (or MAX{PCMAXL_DW(P, Q), PCMAXL_DW(Q, (P+1))} or MIN {PCMAX_DW(P, Q),PCMAX_DW(Q, (P+1))} or MAX {PCMAX_DW(P, Q), PCMAX_DW(Q, (P+1))} orPCMAXL_DW(P, Q) or PCMAXL_DW(Q, (P+1)) or PCMAX_DW(P, Q) or PCMAX_DW(Q,(P+1))). Further, for example, MAX_WANVAL may be determined as MAX{WAN_TXP(P), WAN_TXP(P+1)}. Furthermore, for example, NEW_VAL related todetermining of D2D_TXP(Q) may be replaced with P_(PowerClass) or MIN{P_(EMAX,A), P_(PowerClass)}.

For example, if TX power of a D2D signal at the SF # Q of the Cell # A,which is determined by an open-loop power control parameter, is assumedas “D2D_CONP(Q+1)”, TX power of a final D2D signal at a correspondingtime(“D2D_TXP(Q+1)”) may be determined as MIN {(NEW_VAL−MAX_WANVAL), MIN{PCMAX,A((Q+1), (Q+1)), D2D_CONP(Q+1)}}. Herein, for example, NEW_VALmay be determined as MIN {PCMAXL_WO(P+1), PCMAXL_DW((P+1), (Q+1))} (orMAX {PCMAXL_WO(P+1), PCMAXL_DW((P+1), (Q+1))} or MIN {PCMAX_WO(P+1),PCMAX_DW((P+1), (Q+1))} or MAX {PCMAX_WO(P+1), PCMAX_DW((P+1), (Q+1))}or PCMAXL_WO(P+1) or PCMAXL_DW((P+1), (Q+1)) or PCMAX_WO(P+1) orPCMAX_DW((P+1), (Q+1))). Further, for example, MAX_WANVAL may bedetermined as WAN_TXP(P+1).

Furthermore, for example, NEW_VAL related to determining of D2D_TXP(Q+1)may be replaced with P_(PowerClass) or MIN {P_(EMAX,A), P_(PowerClass)}.

For another example, if TX power of a D2D signal at the SF # Q of theCell # A, which is determined by an open-loop power control parameter,is assumed as “D2D_CONP(Q)”, TX power of a final D2D signal at acorresponding time(“D2D_TXP(Q)”) may be determined as MIN{(NEW_VAL−MAX_WANVAL), MIN {PCMAX,A(Q, Q), D2D_CONP(Q)}}. Herein, forexample, NEW_VAL may be determined as MIN {PCMAXL_DW(P, Q), MIN{PCMAXL_DW(Q, (P+1)), PCMAXL_DW((P+1), (Q+1))} }(or MAX {PCMAXL_DW(P,Q), MIN {PCMAXL_DW(Q, (P+1)), PCMAXL_DW((P+1), (Q+1))}} or MIN{PCMAX_DW(P, Q), MIN {PCMAX_DW(Q, (P+1)), PCMAX_DW((P+1), (Q+1))}} orMAX {PCMAX_DW(P, Q), MIN {PCMAX_DW(Q, (P+1)), PCMAX_DW((P+1), (Q+1))}}or PCMAXL_DW(P, Q) or MIN {PCMAXL_DW(Q, (P+1)), PCMAXL_DW((P+1), (Q+1))}or PCMAX_DW(P, Q) or MIN {PCMAX_DW(Q, (P+1)), PCMAX_DW((P+1), (Q+1))}.Further, for example, MAX_WANVAL may be determined as MAX {WAN_TXP(P),WAN_TXP(P+1)}. Furthermore, for example, NEW_VAL related to determiningof D2D_TXP(Q) may be replaced with P_(PowerClass) or MIN {P_(EMAX,A),P_(PowerClass)}.

For another example, if TX power of a D2D signal at the SF # Q of theCell # A, which is determined by an open-loop power control parameter,is assumed as “D2D_CONP(Q+1)”, TX power of a final D2D signal at acorresponding time(“D2D_TXP(Q+1)”) may be determined as MIN{(NEW_VAL−MAX_WANVAL), MIN {P_(CMAX,A)((Q+1), (Q+1)), D2D_CONP(Q+1)}}.Herein, for example, NEW_VAL may be determined as MIN {MIN{PCMAXL_WO(P+1), PCMAXL_DW(Q, (P+1))}, PCMAXL_DW((P+1), (Q+1))} (or MAX{MIN {PCMAXL_WO(P+1), PCMAXL_DW(Q, (P+1))}, PCMAXL_DW((P+1), (Q+1))} orMIN {MIN {PCMAX_WO(P+1), PCMAX_DW(Q, (P+1))}, PCMAX_DW((P+1), (Q+1))} orMAX {MIN {PCMAX_WO(P+1), PCMAX_DW(Q, (P+1))}, PCMAX_DW((P+1), (Q+1))} orMIN {PCMAXL_WO(P+1), PCMAXL_DW(Q, (P+1))} or PCMAXL_DW((P+1), (Q+1)) orMIN {PCMAX_WO(P+1), PCMAX_DW(Q, (P+1))} or PCMAX_DW((P+1), (Q+1)).Further, for example, MAX_WANVAL may be determined as WAN_TXP(P+1).Furthermore, for example, NEW_VAL related to determining of D2D_TXP(Q+1)may be replaced with P_(PowerClass) or MIN {P_(EMAX,A), P_(PowerClass)}.

For example, if D2D_TXP(Q) and D2D_TXP(Q+1) cannot satisfy an emissionrequirement pre-defined (or signaled) in a simultaneous transmissionsituation of a WAN UL signal/D2D signal, a rule may be defined such thatD2D_TXP(Q) and D2D_TXP(Q+1) are preferentially decreased until theemission requirement is satisfied. For another example, in order tosolve such a problem, a rule may be defined such that a pre-defined (orsignaled) power offset value is additionally applied to (final)D2D_TXT(Q) and/or D2D_TXP(Q+1). For another example, if D2D_TXP(Q) andD2D_TXP(Q+1) cannot satisfy the pre-defined (or signaled) emissionrequirement in the simultaneous transmission situation of the WAN ULsignal/D2D signal, a rule may be defined such that transmission of theD2D signal is omitted.

FIG. 17 shows timing of D2D signal transmission and WAN UL signaltransmission.

Referring to FIG. 17, an SF # Q+1 of a Cell # A and an SF # P+1 of aCell # B are not aligned temporally. In this situation, D2D signaltransmission is performed in an SF # Q and SF # Q+1 of the Cell # A, andWAN UL signal transmission is performed in the SF # P+1 of the Cell # B.

Example #5-8

In ‘CASE (2)’ or timing as shown in FIG. 17, for example, if D2D signaltransmission, D2D signal transmission, and WAL UL signal transmissionmust be sequentially performed on the SF # Q of the Cell # A, the SF#(Q+1) of the Cell # A, and the SF3(P+1) of the Cell # B, it may bedefined such that TX power of a D2D signal in the SF # Q of the Cell # Aand TX power of a D2D signal in the SF #(Q+1) of the Cell # A aredetermined according to the following rule.

Herein, for example, (Example #5-8) may be interpreted as a case where aWAN UL cell (carrier) leads a D2D cell (carrier). Further, for example,in FIG. 17, an SF index ‘Q (/(Q+1))’ of the Cell # A may be assumed as‘K (/(K+1))’, and an SF index ‘(P+1)’ of the Cell # B may be assumed as‘(K+1)’.

At a (partially or entirely) overlapping time (subframe) on other cells,the TX power of the D2D signal in the SF # Q of the Cell # A and the TXpower of the D2D signal in the SF #(Q+1) of the Cell # A may bedetermined on the basis of P_(CMAX)(P+1)(“PCMAX_WO(P+1)”) (orP_(CMAX_L)(P+1) (“PCMAXL_WO(P+1)”)) or P_(CMAX,B)(P+1) related to WAN ULsignal transmission in the SF #(P+1) of the Cell # B, calculated underthe assumption that there is no D2D signal transmission.

For example, if the TX power of the WAN UL signal in the SF #(P+1) ofthe Cell # B determined by the open-loop power control/closed-loop powercontrol parameter is assumed as “WAN_CONP(P+1)”, the final TX power ofthe WAN UL signal in the SF #(P+1) of the Cell # B (“WAN_TXP(P+1)”) maybe determined as MIN {PCMAX_WO(P+1), MIN {P_(CMAX,B)(P+1),WAN_CONP(P+1)}}.

Under the assumption that WAN UL signal transmission in the SF #(P+1) ofthe Cell # B partially overlaps with a pre-defined (or signaled) WAN ULsignal transmitted in the SF # Q of the Cell # A (according to anallocated-resource count/position/modulation related to D2D signaltransmission), TX power for a D2D signal in the SF # Q of the Cell # Aand TX power of a D2D signal in the SF #(Q+1) of the Cell # A may bedetermined on the basis of calculated P_(CMAX)(Q, (P+1)) related to D2Dsignal transmission in the SF # Q of the Cell # A (“PCMAX_DW(Q, (P+1))”)(or P_(CMAX_L)(Q, (P+1)) (“PCMAXL_DW(Q, (P+1))”)) or P_(CMAX,A)(Q,(P+1)). In this rule, WAN UL signal transmission (in the SF #(P+1) ofthe Cell # B) may be interpreted as a reference for calculating D2Dsignal TX power (in the SF # Q of the Cell # A) (e.g., PCMAX_DW(Q,(P+1)) (or PCMAXL_DW(Q, (P+1)))).

Under the assumption that WAN UL signal transmission in the SF #(P+1) ofthe Cell # B partially overlaps with a pre-defined (or signaled) WAN ULsignal transmitted in the SF #(Q+1) of the Cell # A according to anallocated-resource count/position/modulation related to D2D signaltransmission, TX power for a D2D signal in the SF # Q of the Cell # Aand TX power of a D2D signal in the SF #(Q+1) of the Cell # A may bedetermined on the basis of calculated P_(CMAX)((P+1), (Q+1)) related toD2D signal transmission (in the SF #(Q+1) of the Cell # A)(“PCMAX_DW((P+1), (Q+1))”) (or P_(CMAX_L)((P+1), (Q+1))(“PCMAXL_DW((P+1), (Q+1))”)) or P_(CMAX,A)((P+1), (Q+1)). Herein, forexample, in this rule, WAN UL signal transmission (in the SF #(P+1) ofthe Cell # B) may be interpreted as a reference for calculating D2Dsignal TX power (in the SF #(Q+1) of the Cell # A) (e.g.,PCMAX_DW((P+1), (Q+1)) (or PCMAXL_DW((P+1), (Q+1)))).

For example, if TX power of a D2D signal in the SF # Q of the Cell # Adetermined by an open-loop power control parameter is assumed as“D2D_CONP(Q)”, TX power of a final D2D signal at a correspondingtime(“D2D_TXP(Q)”) may be determined as MIN {(NEW_VAL−MAX_WANVAL), MIN{P_(CMAX,A)(Q, (P+1)), D2D_CONP(Q)}}. Herein, for example, NEW_VAL maybe determined as MIN {PCMAXL_WO(P+1), PCMAXL_DW(Q, (P+1))} (or MAX{PCMAXL_WO(P+1), PCMAXL_DW(Q, (P+1))} or MIN {PCMAX_WO(P+1), PCMAX_DW(Q,(P+1))} or MAX {PCMAX_WO(P+1), PCMAX_DW(Q, (P+1))} or PCMAXL_WO(P+1) orPCMAXL_DW(Q, (P+1)) or PCMAX_WO(P+1) or PCMAX_DW(Q, (P+1)). Further, forexample, MAX_WANVAL may be determined as WAN_TXP(P+1). Furthermore, forexample, NEW_VAL related to determining of D2D_TXP(Q) may be replacedwith P_(PowerClass) or MIN {P_(EMAX,A), P_(PowerClass)}.

For example, if TX power of a D2D signal in the SF #(Q+1) of the Cell #A determined by an open-loop power control parameter is assumed as“D2D_CONP(Q+1)”, TX power of a final D2D signal at a correspondingtime(“D2D_TXP(Q+1)”) may be determined as MIN {(NEW_VAL−MAX_WANVAL), MIN{P_(CMAX,A)((P+1), (Q+1)), D2D_CONP(Q+1)}}. Herein, for example, NEW_VALmay be determined as MIN {PCMAXL_WO(P+1), PCMAXL_DW((P+1), (Q+1))} (orMAX {PCMAXL_WO(P+1), PCMAXL_DW((P+1), (Q+1))} or MIN {PCMAX_WO(P+1),PCMAX_DW((P+1), (Q+1))} or MAX {PCMAX_WO(P+1), PCMAX_DW((P+1), (Q+1))}or PCMAXL_WO(P+1) or PCMAXL_DW((P+1), (Q+1)) or PCMAX_WO(P+1) orPCMAX_DW((P+1), (Q+1))). Further, for example, MAX_WANVAL may bedetermined as WAN_TXP(P+1).

Furthermore, for example, NEW_VAL related to determining of D2D_TXP(Q+1)may be replaced with P_(PowerClass) or MIN {P_(EMAX,A), P_(PowerClass)}.

For example, if D2D_TXP(Q) and D2D_TXP(Q+1) cannot satisfy an emissionrequirement pre-defined (or signaled) in a simultaneous transmissionsituation of a WAN UL signal/D2D signal, a rule may be defined such thatD2D_TXP(Q) and D2D_TXP(Q+1) are preferentially decreased until theemission requirement is satisfied. For another example, in order tosolve such a problem, a rule may be defined such that a pre-defined (orsignaled) power offset value is additionally applied to (final)D2D_TXT(Q) and/or D2D_TXP(Q+1). For another example, if D2D_TXP(Q) andD2D_TXP(Q+1) cannot satisfy the pre-defined (or signaled) emissionrequirement in the simultaneous transmission situation of the WAN ULsignal/D2D signal, a rule may be defined such that transmission of theD2D signal is omitted.

For example, by applying some or all of methods described below, a rulemay be defined such that TX power of a D2D signal is derived/determined.

The following rules may be limitedly applied only to a UE which iscapable of both discovery and D2D communication, or a UE whichsimultaneously performs discovery signal transmission and D2Dcommunication transmission or to which both of the discovery and the D2Dcommunication are configured via higher layer signaling, or a UE whichis capable of only the discovery (a UE which performs only the discoverytransmission or to which only the discovery is configured via the higherlayer signaling), or a UE which is capable of only the D2D communication(or a UE which performs only the D2D communication transmission or towhich only the D2D communication is configured via the higher layersignaling).

Further, for example, in the following rules, TX power of a PSSS (and/orPSBCH) (related to discovery and/or D2D communication) transmitted by aUE which is capable of both discovery and D2D communication (or a UEwhich simultaneously performs discovery signal transmission and D2Dcommunication transmission or to which both of the discovery and the D2Dcommunication are configured via higher layer signaling) or a UE whichis capable of only the discovery (or a UE which performs only thediscovery transmission or to which only the discovery is configured viathe higher layer signaling), or a UE which is capable of only the D2Dcommunication (or a UE which performs only the D2D communicationtransmission or to which only the D2D communication is configured viathe higher layer signaling) may calculate a value P_(CMAX,C)(N) (and/orP_(CMAX)(N)) used when determining the TX power of the PSSS (and/orPSBCH) (related to discovery and/or D2D communication) by substitutingMIN {a maximum D2D communication TX power value, a maximum discovery TXpower value} (or MAX {a maximum D2D communication TX power value, amaximum discovery TX power value} or a maximum D2D communication TXpower value or a maximum discovery TX power value) to a parameterP_(EMAX,C) according to: 1) whether there is an SIB 19 and/or an SIB 18;and 2) whether there is ‘syncConfig’ of D2D communication and/or‘syncConfig’ of discovery (or whether decoding is possible).

Hereinafter, it is described a method for preventing D2D TX power fromhaving an effect on TX power of WAN UL transmission when WAN ULtransmission and D2D transmission (sidelink transmission) are performedin different carriers.

At present, transmit power of a sidelink channel and a sidelink signalis determined to a smaller value between an output value based on anopen-loop power control and a maximum power value. For example, transmitpower for a PSSCH according to a mode 2 may be determined by thefollowing equation.P _(PSSCH)=min{P _(CMAX,PSSCH),10 log₁₀(M _(PSSCH))+P_(O_SSCH,1)+α_(PSSCH,2)·PL} [dBm]  [Equation 26]

In the above equation, P_(CMAX,PSSCH) is a value P_(CMAX,c) determinedby a UE as to a UL subframe corresponding to a sidelink subframe inwhich a PSSCH is transmitted. M_(PSSCH) is a band of PSSCH resourceallocation expressed by the number of resource blocks, and PL denotes apath loss value.

Herein, P_(CMAX,c) is determined using various parameters, and one ofthe parameters is P_(EMAX). P_(EMAX) is a value given by P-Max which isan information element defined in an SIB 1.

Meanwhile, there is an ongoing discussion on parameters for configuringmaximum power for D2D transmission. Examples of the parameter mayinclude ‘discMaxTxPower’, ‘maxTxPower’, or the like. The‘discMaxTxPower’ may be included in an information element (IE) called‘ProseDiscTxPowerInfo’ for discovery, and the ‘maxTxPower’ may beincluded in an IE called ‘ProsePreconfiguration’ for D2D communicationoutside cell coverage.

To complete a process of determining sidelink TX power by the UE, thereis a need to define P_(CMAX,c) for each sidelink channel/signal.

In one method for this, P_(EMAX) which is a configurable parameter isgiven as a parameter value related to corresponding sidelinktransmission.

As described above, when calculating P_(CMAX,c) for PSDCH, a valueindicated by ‘discMaxTxPower’ is set to a value P_(EMAX). Further, whencalculating P_(CMAX,c) for PSCCH and PSSCH outside cell coverage, avalue indicated by ‘maxTxPower’ is set to the value P_(EMAX). In thisstate, there is no configuration for D2D communication inside the cellcoverage, and P-Max which is an existing parameter is re-used.

Meanwhile, how to determine maximum power of SLSS and PSBCH is a matterto be considered. Since there is no particular parameter to beconfigured for this usage, it may be required to re-use parameters usedin other sidelink channels.

Herein, parameters used in a sidelink channel which triggers SLSS/PSBCHtransmission and a parameter for the SLSS/PSBCH transmission may bepreferably used in the same manner. This is because coverage ofSLSS/PSBCH may be similar to coverage of the sidelink channel whichtriggers the SLSS/PSBCH.

If not using the same parameter, the SLSS/PSBCH and the sidelink channelwhich triggers this may have different coverage. For example, if theSLSS/PSBCH always uses P-Max included in an SIB1, the coverage of theSLSS may be a bottleneck of discovery when a network supporting only thediscovery desires to restrict maximum power of PUSCH by consideringinter-cell interference.

Meanwhile, when a UE inside cell coverage transmits both of D2Dcommunication and discovery, SLSS/PSBCH transmission in a subframe maybe simultaneously triggered by the D2D communication and the discovery.In this case, the following two methods may be considered.

1. A first method is for taking a maximum value between ‘discMaxTxPower’and ‘P-Max’. This method has an advantage in that SLSS/PSBCH can coverboth of D2D discovery and D2D communication. However, this method has aproblem in that S-RSRP is changed since a maximum power parameter forPSBCH can be changed in a discovery resource pool-related SLSS subframein which a specific UE transmits a discovery signal.

In the following discussion, it is assumed that an SLSS triggeringcondition is changed in unit of subframes. For example, SLSStransmission may be triggered by both of D2D communication and discoveryin a 1st SF, and SLSS transmission may be triggered only by the D2Dcommunication in a 2nd SF. For example, a subframe which is a 1st SF ofa resource pool for discovery signal transmission and which is includedin a physical sidelink control channel (PSCCH) for D2D communicationtransmission may be the 1st SF. Further, SLSS may be triggered after 40ms (for only the D2D communication) by only the D2D communication, and asubframe in this case may be the 2nd SF.

2. A second method is for taking a value P-Max. According to thismethod, there is an advantage in that an S-RSRP change can be avoided.

3. A third method is for taking a value ‘discMaxTxPower’.

To solve a problem in which a coverage difference occurs between thePSDCH and the SLSS/PSBCH, a network may increase the value P-Max byconsidering coverage of D2D communication and maximum power of PUSCH,thereby solving the problem.

If maximum power of sidelink transmission is denoted by P_(CMAX,c), itmay be obtained by configuring P_(EMAX) as follows.

TABLE 5 Maximum power Condition Value set to P_(EMAX) P_(CMAX, PSSCH),Out-coverage maxTxPower in ProsePreconfiguration IE P_(CMAX, PSCCH)In-coverage P-Max in SIB1 P_(CMAX, PSDCH) In-coverage discMaxTxPower inProseDiscTxPowerInfo IE P_(CMAX, PSSS) Out-coverage maxTxPower inProsePreconfiguration IE In-coverage and P-Max in SIB1 triggered forcommunication Otherwise discMaxTxPower in ProseDiscTxPowerInfo IE

Herein, being triggered for D2D communication implies that SLSS/PSBCHtransmission in a specific subframe is triggered for the followingcases.

1) When a UE is capable of performing D2D communication and a basestation instructs SLSS/PSBCH transmission to the UE via a dedicatedsignal, and 2) when RSRP of a serving cell is lower than a thresholdconfigured for SLSS/PSBCH transmission, and PSCCH or PSSCH istransmitted in a PSCCH period included in subframes for SLSS/PSBCHtransmission.

Meanwhile, if power is restricted when operating multiple carriers, D2DTX power in a sidelink subframe may be decreased to a specific powerlevel so as not to have an effect on WAN UL TX power. The UE maydecrease D2D TX power when a result of summing calculated TX power ofeach channel exceeds supportable maximum power.

It is considered a case where D2D transmission occurs only in onecarrier.

Hereinafter, {circumflex over (P)}_(UL)(i) is a sum of UL TX power in aUL subframe i in carriers other than a carrier c. The sum of UL TX powermay be obtained under the control of the existing WAL UL power. This iscalculated without consideration of sidelink transmission in the carrierc.

Herein, for example, among the remaining carriers (in which WAN ULtransmission is performed) other than a Carrier # C (i.e., a carrier inwhich sidelink transmission is performed), if PUSCH transmission (i.e.,performed with TX power of P_PUSCH) and SRS transmission (i.e.,performed with TX power of P_SRS) are simultaneously performed (orconfigured) on a subframe i of a specific Carrier # X, when calculating{circumflex over (P)}_(UL)(i), a rule may be defined such that WAN UL TXpower in the subframe i of the Carrier # X is regarded (or assumed) as amaximum value (or minimum value) between P_PUSCH and P_SRS.

For another example, among the remaining carriers (in which WAN ULtransmission is performed) other than a Carrier # C (i.e., a carrier inwhich sidelink transmission is performed), if PUCCH transmission (i.e.,performed with TX power of P_PUCCH) and SRS transmission (i.e.,performed with TX power of P_SRS) are simultaneously performed (orconfigured) on a subframe i of a specific Carrier # Y, when calculating{circumflex over (P)}_(UL)(i), a rule may be defined such that WAN UL TXpower in the subframe i of the Carrier # Y is regarded (or assumed) as amaximum value (or minimum value) between P_PUCCH and P_SRS.

Herein, for example, simultaneous transmission of PUCCH and SRS on thesubframe i of the Carrier # Y may be interpreted as a case wheresimultaneous transmission of HARQ-ACK and SRS is configured (in theCarrier # Y) (or a case where a shortened PUCCH format is configured).

{circumflex over (P)}_(SL,c)(k) is a resultant value of a sidelink TXpower control for a subframe k in a carrier c under the assumption thatthere is no UL transmission temporally overlapping in the remainingcarriers other than the carrier c.

{circumflex over (P)}_(SL,c)(k,i) denotes power which can be used insidelink transmission in a subframe k of a carrier c. It is premisedherein that a UL subframe i of another carrier temporally overlaps withthe subframe k.

FIG. 18 shows that a subframe k of a carrier c overlaps with a subframei of a carrier x.

Referring to FIG. 18, the subframe k and the subframe i of differentcarriers, i.e., the carrier c and the carrier x, temporally overlap witheach other. Sidelink transmission, i.e., signal transmission based on aD2D operation, is performed in the subframe k, and WAN UL transmissionis performed in the subframe i.

In a situation of FIG. 18, if ({circumflex over (P)}_(UL)(i)+{circumflexover (P)}_(SL,c)(k)) is less than {circumflex over (P)}_(CMAX)(k,i)which is maximum power that can be supported by the UE, transmission ineach carrier does not have an effect on each other, and additional powerreduction is unnecessary. Herein, {circumflex over (P)}_(CMAX)(k,i) mustbe calculated by considering that WAN UL transmission and sidelinktransmission are performed simultaneously. In this case, it is premisedthat a parameter such as a band combination/modulation/resource or thelike of the sidelink transmission is the same as those of PUSCHtransmission.

If ({circumflex over (P)}_(UL)(i)+{circumflex over (P)}_(SL,c)(k)) isgreater than {circumflex over (P)}_(CMAX)(k,i), sidelink TX power mustbe reduced as shown in the following equation.{circumflex over (P)} _(SL,c)(k,i)=w(k,i)×{circumflex over (P)}_(SL,c)(k)≤({circumflex over (P)} _(CMAX)(k,i)−{circumflex over (P)}_(UL)(i))  [Equation 27]

In the above equation, w(k,i) is a scaling factor, and may be selectedfrom values in the range of 0 to 1.

FIG. 19 shows an example of a case where a sidelink subframe overlapswith a plurality of UL subframes.

Referring to FIG. 19, a subframe k of a carrier c partially overlapstemporally with subframes i and i+1 of a carrier x. Sidelinktransmission is performed in the subframe k, and WAN UL transmission isperformed in subframes i and i+1.

In this case, in order to implement constant sidelink TX power, the UEcalculates {circumflex over (P)}_(SL,c)(k,i) for all UL subframes (i.e.,subframes i and i+1) overlapping with a sidelink subframe k, and takes asmallest one among them. That is, final sidelink TX power is given bythe following equation.min{{circumflex over (P)} _(SL,c)(k,i),{circumflex over (P)}_(SL,c)(k,(i+1))}  [Equation 28]

Now, a method of determining TX power is described in a case wheresidelink transmission (transmission based on a D2D operation) and WAN ULtransmission overlap with each other temporally in different carriers asshown in FIGS. 18 and 19.

FIG. 20 shows a method of determining UL TX power according to anembodiment of the present invention.

Referring to FIG. 20, a UE independently calculates TX power in eachcarrier (S191). For example, TX power is calculated for a carrier Cperforming sidelink transmission, and TX power is calculated for acarrier X performing WAN UL transmission.

If a sum of the independently calculated TX power of each carrier isgreater than supportable maximum power, the UE decreases sidelink TXpower (S192). Herein, sidelink transmission may be treated similarly toWAN UL transmission in another carrier (for example, it is assumed thatparameters related to the sidelink transmission is applied to WAN ULtransmission) to calculate the supportable maximum power (for example,it may be regarded (/interpreted) identically to the existing situationin which WAN UL transmissions occur simultaneously on the carrier C andthe carrier X). In other words, the supportable maximum power iscalculated by regarding sidelink transmission as WAN UL transmission. Itis assumed in this case that the same parameters as the sidelinktransmission are used in the WAN UL transmission.

For example, if TX power for WAN transmission performed in a 1^(st)carrier is denoted as 1^(st) TX power and TX power for transmissionbased on a D2D operation performed in a 2^(nd) carrier is denoted by2^(nd) TX power, the 1^(st) and 2^(nd) TX powers are calculatedindependently, and if a sum of the 1^(st) TX power and the 2^(nd) TXpower is greater than the supportable maximum power of the UE, the2^(nd) TX power is decreased.

In this case, the WAN transmission and the transmission based on the D2Doperation are simultaneously performed, and the 1^(st) carrier and the2^(nd) carrier are carriers of different frequencies.

Further, the supportable maximum power of the UE may be calculated bytreating the transmission based on the D2D operation similarly to theWAN transmission (for example, it may be regarded (/interpreted)identically to the existing situation in which WAN UL transmissionsoccur simultaneously in a 1^(st) carrier and a 2^(nd) carrier).

For example, 2^(nd) TX power is calculated under the assumption thatparameters related to sidelink transmission may be equally applied toWAN UL transmission, and thereafter the supportable maximum power of theUE may be calculated on the basis of (or by using) the 2^(nd) TX powerand 1st TX power.

That is, according to the method of FIG. 20, TX power allocated tosidelink transmission cannot be greater than power which remains insupportable maximum power after allocating power first to WAN ULtransmission. According to this method, for example, allocating ofsidelink transmit power does not have an effect on WAN UL transmission.

Hereinafter, a cell selection and cell reselection operation (on anon-serving carrier/frequency) for D2D communication (in a non-servingcarrier/frequency) and/or a cross-pool configuration operation aredescribed under a situation of intra-PLMN/inter-PLMN.

A requirement described below may be applied to a UE in an RRC_IDLEstate and an RRC_CONNECTED state. When the UE intends to perform D2Dcommunication at a non-serving frequency, a measurement is performed forthe non-serving frequency for the purpose of a cell selection and anintra-frequency reselection. If the UE detects at least one cell whichsatisfies an S-criterion at the frequency configured to perform the D2Dcommunication, it is regarded that the UE is inside cell coverage at thefrequency in regards to the D2D communication. If the UE cannot detectany cell satisfying the S-criterion at the frequency, it is regardedthat the UE is outside the cell coverage in regards to the D2Dcommunication.

Upon selecting a cell in the non-serving frequency for the D2Dcommunication, the UE may perform an intra-frequency reselection processfor selecting a better cell for the D2D communication at the frequency.In this case, the reselection process may be performed according toreselection related parameters which are broadcast in the cell selectedfor the D2D communication.

It may be regarded that a carrier predetermined for D2D communicationhas a highest cell reselection priority.

If a frequency configured for D2D communication is a serving frequency,the UE uses a serving cell of the frequency for the D2D communication.

In an intra PLMN case, it may be allowed to configure that a discoverysignal is transmitted in other carriers via an RRC signal. The RRCsignal may be used for a type 1 or type 2 discovery configuration for afrequency other than a primary frequency.

In an inter-PLMN case, there is a need for an SA2 guideline for whetheran inter-PLMN authentication for discovery signal transmission iscontrolled by a higher layer.

If a network has inter-PLMN information, the network may configure a UEsimilarly to the intra-PLMN case. An inter-PLMN coordination is notalways possible. In case of non-coordinated inter-PLMN, the UE may readan SIB19 of a corresponding frequency to know a transmission/receptionresource in use.

When there is no base station at a frequency at which a D2D operation isperformed, a D2D discovery operation may be supported outside cellcoverage.

Hereinafter, a frequency/carrier (referred to as non-primaryfrequency/carrier) other than a primary frequency of a UE whichtransmits a specific D2D signal (and/or a non-serving carrier/frequency)is denoted by “NP_FRQ”. It is proposed a method of effectivelyconfiguring D2D TX power when performing an operation of transmitting aD2D channel/signal on the “NP_FRQ”.

Herein, a primary carrier/frequency (and/or a serving carrier/frequency)of a UE which transmits a D2D signal is denoted by “PR_FRQ”. NP_FRQ mayhave an inter-PLMN (or intra-PLMN) and/or inter-frequency (orintra-frequency) (and/or an adjacent frequency (or the same frequency))relation with the PR_FRQ.

[Proposed method #6] Estimating of a path loss (PL) related to anon-serving cell on NP_FRQ may be inaccurate in comparison withestimating of a PL related to a serving cell on PR_FRQ in variousreasons. (1) This is because the number of measurement samples relatedto the non-serving cell on NP_FRQ which can be acquired within aspecific time period may be relatively smaller than the number ofmeasurement samples related to the serving cell on PR_FRQ. Herein, forexample, in case of D2D signal transmission of a UE which moves fast,even NP_FRQ non-serving cell related measurement samples which areacquired in a relatively less amount may be inaccurate. Therefore, agreater amount of time (and measurement sample) may be required tosatisfy a pre-defined (or signaled) measurement requirement. (2)Further, this is because estimating of a PL for determining powerrelated to a D2D channel/signal transmission operation in NP_FRQ may bedefined as a pre-defined (or signaled) different cell (on acarrier/frequency) other than the NP_FRQ non-serving cell.

For example, the inaccurate estimating of the PL related to the NP_FRQnon-serving cell results in inaccurate determining of D2D channel/signalTX power on NP_FRQ, and this may result in undesired interference on WAN(UL/(/DL)) communication (and/of D2D communication) of a non-servingcell (and/or a serving cell (e.g., when NP_FRQ and PR_FRQ have anadjacent frequency relation)) (e.g., when NP_FRQ D2D TX power is set tobe excessively high), or may result in a deterioration of D2Dchannel/signal transmission performance on NP_FRQ (e.g., when the NP_FRQD2D TX power is set to be excessively low).

In order to reduce such a problem, it may be configured such that a UEwhich performs an operation of transmitting an NP_FRQ D2D channel/signalis allowed to conform to the following (some or all of) rules.

Herein, a power control parameter related to D2D channel/signaltransmission may be interpreted as an open-loop/closed-loop powercontrol parameter and/or maximum (allowed) D2D TX power.

(Rule #6-1) When a power control parameter related to NP_FRQ D2Dchannel/signal transmission (i.e., named as “NPPCPARA_SV”) is signaled(or configured) by a serving cell on PR_FRQ, a UE which transmits a D2Dsignal may determine NP_FRQ D2D channel/signal TX power on the basis ofthe NPPCPARA_SV by ignoring a power control parameter (i.e., named as“NPPCPARA_NS”) (related to NP_FRQ D2D channel/signal transmission)acquired (through pre-defined signal reception (e.g., SIB)) from theNP_FRQ non-serving cell.

Herein, for example, if NPPCPARA_SV is not signaled (or configured) by aserving cell on PR_FRQ, the UE is allowed to determine NP_FRQ D2Dchannel/signal TX power on the basis of the NPPCPARA_NS (acquired(through pre-defined signal reception) from an NP_FRQ non-serving cell).

A channel (e.g., SIB) for announcing PR_FRQ related D2D channel/signalresource pool information and/or D2D channel/signal TX power information(or D2D channel/signal resource pool information and/or D2Dchannel/signal TX power information on a carrier (or frequency) havingan intra-frequency (or intra-PLMN) with PR_FRQ) and a channel (e.g.,SIB) for announcing NP_FRQ related D2D channel/signal resource poolinformation and/or D2D channel/signal TX power information (or D2Dchannel/signal resource pool information and/or D2D channel/signal TXpower information on a carrier (or frequency) having an inter-frequency(or inter-PLMN) relation with PR_FRQ) may be independently (ordifferently) defined.

(Rule #6-2) Two (usages of) power control parameters are signaled by anNP_FRQ non-serving cell via a pre-defined channel (/signal) (e.g., SIB).One (i.e., named as “SV_PARA”) may be used by a UE which measures a pathloss by using it as a serving cell (or intra-frequency), and the other(i.e., named as “NS_PARA”) may be used by a UE which measures a path byusing it as a non-serving cell (or inter-frequency).

Herein, for another example, SV_PARA and a (power control parameter)offset (i.e., a UE which measures a path loss by using it as anon-serving cell (or inter-frequency) determines final NP_FRQ D2D TXpower by applying a corresponding (power control parameter) offset tothe SV_PARA) may be signaled (or a UE which measures a path loss byusing it as a serving cell (or intra-frequency) determines final NP_FRQD2D TX power by applying a corresponding (power control parameter)offset to the NS_PARA) may be signaled) by an NP_FRQ non-serving cellvia a pre-defined channel (/signal) (e.g., SIB).

For another example, a serving cell on PR_FRQ (or a non-serving cell onNP_FRQ) may be configured (through pre-defined signaling) to applyrelatively small TX power (and/or D2D transmission possibility) to a UEwhich has a relation thereto (or which exists inside its coverage) whenperforming D2D channel/signal transmission on an inter-PLMN carrier(frequency) (or inter-frequency). This may be interpreted as a sort ofpenalty.

Further, for example, a serving cell on PR_FRQ (or a non-serving cell onNP_FRQ) may be configured to apply relatively small TX power (and/or D2DTX probability) (through pre-defined signaling) when a UE which has aconnection with an inter-PLMN (or inter-frequency) cell (or inter-PLMN(or inter-frequency) cell (or which exists inside coverage of aninter-PLMN (or inter-frequency cell)) intends to perform its(inter-PLMN) carrier/frequency (or on an intra-frequency/carrier). Thismay be interpreted as a sort of penalty.

Hereinafter, a PSDCH transmission and PSDCH related SLSS transmissionmethod will be described in case of partially being included in cellcoverage or of being outside the cell coverage.

Assume that a UE operating based on LTE-A Rel-13 is an Rel-13 UE. TheRel-13 UE transmits a type-1 discovery signal according to any one ofthe following two operations (i.e., an operation 1, an operation 2) whenSLSS is transmitted.

Operation 1: In the same operation as Rel-12, the UE transmits the SLSSin a subframe n determined according to an Rel-12 operation in eachdiscovery period.

Operation 2: The UE transmits the SLSS every 40 ms in each discoveryperiod. Real SLSS transmission depends on Rel-12 conditions such as aWAN priority. The UE also transmits a PSBCH in a subframe in which theSLSS is transmitted. In this case, the same content as the PSBCH for theUE for performing D2D communication based on Rel-13 may be used.

The Rel-13 UE outside the cell coverage conforms to the operation 2described above in SLSS transmission when transmitting a type-1 publicsafety (PS) discovery signal.

The Rel-13 UE inside the cell coverage conforms to the operation 1 for acase of transmitting the discovery signal for a usage other than publicsafety in SLSS transmission when transmitting a discovery signal. On theother hand, in case of transmitting a discovery signal for a usage ofpublic safety, a base station may configure the operation 1 or theoperation 2, and the UE conforms thereto.

A UE which participates in discovery signal transmission for the usageof public safety and which uses the operation 2 transmits SLSS every 40ms. In this case, the UE may transmit the SLSS continuously wheneverthere is a discovery message given from a higher layer and to betransmitted in a given carrier.

The UE which participates in discovery signal transmission for the usageof public safety and which uses the operation 2 may reuse PSBCH which isused in D2D communication based on Rel-12. That is, the same content maybe included. A UE which uses the operation 1 does not transmit thePSBCH.

Parameters for PSCCH/PSSCH transmission and PSCCH/PSSCH related SLSStransmission for the UE outside the cell coverage may be configuredthrough a pre-defined signal (e.g., SIB).

The following table shows an example of predetermined parameters for asidelink.

TABLE 6 -- ASN1START SL-Preconfiguration-r12 ::= SEQUENCE {   preconfigGeneral-r12       SL-PreconfigGeneral-r12,   preconfigSync-r12       SL-PreconfigSync-r12,    preconfigComm-r12      SL-PreconfigCommPoolList4-r12,    ... } SL-PreconfigGeneral-r12::= SEQUENCE {    -- PDCP configuration    rohc-Profiles-r12         SEQUENCE {       profile0x0001-r12             BOOLEAN,      profile0x0002-r12             BOOLEAN,       profile0x0004-r12            BOOLEAN,       profile0x0006-r12             BOOLEAN,      profile0x0101-r12             BOOLEAN,       profile0x0102-r12            BOOLEAN,       profile0x0104-r12             BOOLEAN    },   -- Physical configuration    carrierFreq-r12    ARFCN-ValueEUTRA-r9,   maxTxPower-r12       P-Max,    additionalSpectrumEmission-r12   AdditionalSpectrumEmission,    sl-bandwidth-r12    ENUMERATED {n6,n15, n25, n50, n75, n100},    tdd-ConfigSL-r12    TDD-ConfigSL-r12,   reserved-r12    BIT STRING (SIZE (19)),    ... } SL-PreconfigSync-r12::=  SEQUENCE {    syncCP-Len-r12    SL-CP-Len-r12,syncOffsetIndicator1-r12    SL-OffsetIndicatorSync-r12,   syncOffsetIndicator2-r12    SL-OffsetIndicatorSync-r12,   syncTxParameters-r12    P0-SL-r12,    syncTxThreshOoC-r12   RSRP-RangeSL3-r12,    filterCoefficient-r12    FilterCoefficient,   syncRefMinHyst-r12    ENUMERATED {dB0, dB3, dB6, dB9, dB12},   syncRefDiffHyst-r12    ENUMERATED {dB0, dB3, dB6, dB9, dB12, dBinf},   ... } SL-PreconfigCommPoolList4-r12 ::= SEQUENCE (SIZE(1..maxSL-TxPool-r12)) OF SL-PreconfigCommPool-r12SL-PreconfigCommPool-r12 ::= SEQUENCE { -- This IE is same asSL-CommResourcePool with rxParametersNCell absent    sc-CP-Len-r12         SL-CP-Len-r12,    sc-Period-r12          SL-PeriodComm-r12,   sc-TF-ResourceConfig-r12       SL-TF-ResourceConfig-r12,   sc-TxParameters-r12          P0-SL-r12,    data-CP-Len-r12            SL-CP-Len-r12,    data-TF-ResourceConfig-r12      SL-TF-ResourceConfig-r12,    dataHoppingConfig-r12      SL-HoppingConfigComm-r12,    dataTxParameters-r12       P0-SL-r12,   trpt-Subset-r12       SL-TRPT-Subset-r12,    ... } END -- ASN1STOP

In the above table, ‘carrierFreq’ indicates a carrier frequency for asidelink operation. In an FDD case, this indicates an uplink frequency,and its corresponding downlink frequency may be determined by a defaultTX-RX frequency separation.

‘preconfigComm’ indicates a list of the number of individual resourcepools. This may be used in signal transmission/reception for D2Dcommunication.

‘syncRefDiffHyst’ is a hysteresis used when a reference UE forsynchronization is evaluated using a relative comparison.‘syncRefMinHyst’ is a hysteresis used when the reference UE forsynchronization is evaluated using an absolute comparison.

For example, a rule may be defined such that a maximum TX power valuerelated to PDSCH transmission of the UE outside the cell coverage (e.g.,P_(CMAX,PSDCH)) (and/or a maximum TX power value (e.g., P_(CMAX,PSBCH),P_(CMAX,SSSS)) related to SLSS transmission associated withcorresponding PSDCH) is configured independently (or differently) from amaximum TX power value related to PSCCH (and/or PSSCH) transmission ofthe UE outside the cell coverage (e.g., P_(CMAX,PSCCH), P_(CMAX,PSSCH))(and/or a maximum TX power value related to SLSS transmission associatedwith corresponding PSCCH (and/or PSSCH) (e.g., P_(CMAX,PSBCH),P_(CMAX,SSSS))).

Herein, for example, this rule may be applied limitedly only for a casewhere parameters for PSDCH transmission (and/or SLSS transmissionassociated with corresponding PDSCH) of the UE outside the cell coverageare configured through independent (or different) signaling (e.g., SIB)from parameters for PSCCH (and/or PSSCH) transmission of the UE (and/orSLSS transmission associated with corresponding PSCCH (and/or PSSCH)).

Herein, for example, in the proposed rule, the “maximum TX power value”can be extensively interpreted as an “open-loop power control parametervalue (e.g., P_(O), alpha)”.

For another example, a rule may be defined such that a maximum TX powervalue related to public safety (PS) PSDCH transmission of the UE insidethe cell coverage (e.g., P_(CMAX,PSDCH)) (and/or a maximum TX powervalue related to SLSS transmission associated with corresponding PSPSDCH (e.g., P_(CMAX,PSBCH), P_(CMAX,SSSS))) is configured independently(or differently) from a maximum TX power value related to non-PS PSDCHtransmission of the UE inside the cell coverage (e.g., P_(CMAX,PSDCH))(and/or a maximum TX power value related to SLSS transmission associatedwith corresponding non-PS PSDCH (e.g., P_(CMAX,PSBCH), P_(CMAX,SSSS))).That is, it may be interpreted that the maximum TX power value variesdepending on a discovery type.

In the proposed rule, the “maximum TX power value” may be extensivelyinterpreted as an “open-loop power control parameter value (e.g., P_(O),alpha)”.

For another example, a rule may be defined such that a maximum TX powervalue related to relay PDSCH transmission (e.g., P_(CMAX,PSDCH)) (and/ora maximum TX power value related to SLSS transmission associated withcorresponding relay PSDCH (e.g., P_(CMAX,PSBCH), P_(CMAX,SSSS))) isconfigured independently (or differently) from a maximum TX power valuerelated to non-relay PDSCH (or non-PS PSDCH or member PDSCH belonging togroup) transmission (e.g., P_(CMAX,PSDCH)) (and/or a maximum TX powervalue related to SLSS transmission associated with correspondingnon-relay PSDCH (or non-PS PSDCH or member PSDCH belonging to group)(e.g., P_(CMAX,PSBCH), P_(CMAX,SSSS))). That is, it may be interpretedthat the maximum TX power value varies depending on a discovery type.

In the proposed rule, the “maximum TX power value” may be extensivelyinterpreted as an “open-loop power control parameter value (e.g., P_(O),alpha)”.

For another example, a UE which performs a D2D operation is allowed toapply PSDCH maximum TX power signaled (e.g., SIB or dedicated RRCsignal) from a base station (and/or SLSS maximum TX power (associatedwith corresponding PSDCH)) to PDSCH inside the cell coverage (and/or anSLSS (associated with corresponding PSDCH)) when located inside the cellcoverage, and to apply a maximum TX power value corresponding to a(pre-defined (or signaled)) greatest target range to PSDCH outside thecell coverage (and/or SLSS (associated with corresponding PSDCH)) in theabsence of a field related to maximum TX power on pre-defined signaling(e.g., SIB) when located outside the cell coverage. On the other hand, arule may be defined such that a corresponding value is applied to thePSDCH outside the cell coverage (and/or SLSS (associated withcorresponding PSDCH)) in the presence of the field related to themaximum TX power on the pre-defined signaling (e.g., SIB).

For another example, the UE which performs the D2D operation may beconfigured to determine maximum TX power of corresponding SLSStransmission according to some (or all) of priorities described below,when SLSS transmissions triggered from different types of discovery (orPSDCH) transmissions overlap at the same time point.

Herein, for example, the some (or all) of rules described above may belimitedly applied only to a UE which performs a D2D operation inside thecell coverage (and/or a UE which performs the D2D operation outside thecell coverage and/or a UE which performs the D2D operation for a relayrole and/or a separated UE).

Further, for example, if the SLSS transmissions triggered from thedifferent types of discovery (or PSDCH) transmissions do not overlap atthe same time point, it may be defined to conform to each associated,predetermined (or signaled) discovery maximum TX power value.

Further, for example, a base station may be configured such that whichone will be applied among priority rules described below is announced tothe UE through pre-defined signaling (e.g., SIB (a UE in an RRC_IDLEstate, a UE outside the cell coverage), a dedicated signal (a UE in anRRC_CONNECTED state)). In the present proposed method, “SLSS” may beinterpreted, for example, as PSBCH (and/or PSSS (ad/or SSSS)).

Example #1

When SLSS transmission triggered for PS discovery signal transmissionoverlaps with SLSS transmission triggered for non-PS discovery signaltransmission at the same time point, a rule may be defined such thatmaximum TX power of corresponding SLSS is predetermined or conforms tomaximum TX power for a signaled PS discovery signal (or maximum TX powerfor a non-PS discovery signal).

Example #2

When SLSS transmission triggered for discovery of a relay operationoverlaps with SLSS transmission triggered for discovery of a non-relayoperation at the same time point, a rule may be defined such thatmaximum TX power of corresponding SLSS is predetermined or conforms tomaximum TX power for discovery of a signaled relay operation (or maximumTX power for discovery for the non-relay operation). For anotherexample, the SLSS transmission triggered for the discovery of the relayoperation overlaps with SLSS transmission triggered for the discovery ofa group member (or non-PS) at the same time point, a rule may be definedsuch that maximum TX power of corresponding SLSS is predetermined orconforms to maximum TX power of the discovery of the signaled relayoperation (or maximum TX power of the discovery of the group member (ornon-PS)).

For another example, the UE which performs the D2D operation may beconfigured to determine maximum TX power of corresponding SLSStransmission according to some (or all) of priorities described below,when SLSS transmission triggered from discovery (or PSDCH) transmissionoverlaps with SLSS transmission triggered from D2D communication (orPSCCH (and/or PSSCH)) at the same time point.

Herein, for example, the some (or all) of rules described above may belimitedly applied only to a UE which performs a D2D operation inside thecell coverage (and/or a UE which performs the D2D operation outside thecell coverage and/or a UE which performs the D2D operation for a relayrole and/or a separated UE).

Further, a rule may be defined such that a UE which performs a D2Doperation is allowed to conform to each associated predetermined (orsignaled) (discovery/D2D communication) maximum TX power value, whenSLSS transmission triggered from discovery (or PSDCH) transmission doesnot overlap with SLSS transmission triggered from D2D communication (orPSCCH (and/or PSSCH)) transmission at the same time point.

Further, for example, which one will be applied among priority rulesdescribed below may be configured to a UE by a base station. In thiscase, the base station may use defined signaling. An SIB may be used fora UE outside the cell coverage, and a dedicated signal may be used for aUE in an RRC_CONNECTED state. In the present proposed method, the term“SLSS” may be interpreted, for example, as PSBCH (and/or PSSS (ad/orSSSS)).

Example #3

When SLSS transmission triggered by (PS (or non-PS) or relay or groupmember) discovery overlaps with SLSS transmission triggered for D2Dcommunication at the same time point, a rule may be defined such thatmaximum TX power of corresponding SLSS conforms to predetermined (orsignaled) (PS (or non-PS) or relay or group member) discovery maximum TXpower (or D2D communication maximum TX power).

Examples for the aforementioned proposed method may also be included asone of methods for implementing the present invention, and thus can beapparently regarded as a sort of proposed methods. Further, theaforementioned proposed methods may be implemented independently, or mayalso be implemented in a combined (or merged) form of some of theproposed methods.

A rule may be defined such that the aforementioned proposed methods areapplied limitedly only under an environment of an FDD system (and/or TDDsystem). A rule may be defined such that the aforementioned proposedmethods are applied limitedly only to mode-2 D2D communication and/ortype-1 discovery (and/or mode-1 D2D communication and/or type-2discovery).

Further, a rule may be defined such that the aforementioned proposedmethods are applied limitedly only to a UE which performs a D2Doperation inside the cell coverage (and/or a UE which performs the D2Doperation outside the cell coverage) (and/or a UE which performs the D2Doperation in an RRC_CONNECTED state (and/or a UE which performs the D2Doperation in the RRC_CONNECTED state)). A rule may be defined such thatthe aforementioned proposed methods are applied limitedly only to a D2DUE which performs only a D2D discovery (TX(/RX)) operation (and/or a D2DUE which performs only a D2D communication (TX(/RX)) operation).

A rule may be defined such that the aforementioned proposed methods areapplied limitedly only to a scenario in which only D2D discovery issupported (configured) (and/or a scenario in which only D2Dcommunication is supported (configured)).

A rule may be defined such that the aforementioned proposed methods areapplied limitedly only to a case of performing an operation of receivinga D2D discovery signal in different (UL) carriers on an inter-frequency(and/or a case of performing an operation of receiving a D2D discoverysignal in different PLMN (UL) carriers based on inter-PLMN).

Further, for example, a rule may be defined such that the aforementionedproposed methods are applied limitedly only to a case (or time) in whichSLSS/PSBCH transmitted in one subframe are simultaneously triggered byD2D communication and D2D discovery, when a UE transmits both of D2Dcommunication and D2D discovery signals.

FIG. 21 is a block diagram showing a UE according to an embodiment ofthe present invention.

Referring to FIG. 21, a UE 1100 includes a processor 1110, a memory1120, and a radio frequency (RF) unit 1130. The processor 1110implements the proposed functions, procedures, and/or methods. Forexample, the processor 1110 may receive power information discMaxTxPowerfor D2D discovery signal transmission, and may determine transmit powerPPSDCH for the D2D discovery signal transmission on the basis of thepower information discMaxTxPower. Further, the processor 1110 maydetermine TX power for SLSS and PSBCH, and transmits the SLSS and thePSBCH with the determined TX power. If transmission of the SLSS and thePSBCH is triggered simultaneously for both of D2D discovery and D2Dcommunication, the TX power for the SLSS and the PSBCH may be determinedon the basis of power information P-Max for the D2D communication.

The RF unit 1130 is connected to the processor 1110, and sends andreceives radio signals.

The processor may include Application-Specific Integrated Circuits(ASICs), other chipsets, logic circuits, and/or data processors. Thememory may include Read-Only Memory (ROM), Random Access Memory (RAM),flash memory, memory cards, storage media and/or other storage devices.The RF unit may include baseband circuits for processing radio signals.When the embodiment is implemented in software, the aforementionedscheme may be implemented as a module (process or function) thatperforms the aforementioned function. The module may be stored in thememory and executed by the processor. The memory may be placed inside oroutside the processor and may be connected to the processor using avariety of well-known means.

What is claimed is:
 1. A method for transmitting a sidelink discoverysignal in a wireless communication system, the method is performed by auser equipment (UE) and comprising: setting a transmit power for thesidelink discovery signal; and transmitting the sidelink discoverysignal with the transmit power, wherein the transmit power is determinedbased on discMaxTxPower, and wherein based on the UE being configuredwith a range class, the discMaxTxPower informs a parameter used tocalculate a maximum transmit power of the UE configured with the rangeclass.
 2. The method of claim 1, wherein the range class is any one ofshort, medium and long.
 3. The method of claim 1, wherein thediscMaxTxPower is separately provided for each range class configuredfor the UE.
 4. The method of claim 1, further comprising: receiving thediscMaxTxPower from a base station.
 5. The method of claim 4, whereinthe UE transmits the sidelink discovery signal to another UE in a cellcoverage of the base station.
 6. A user equipment (UE) comprising: atransceiver configured to transmit and receive a radio signal; and aprocessor operatively coupled to the transceiver, wherein the processoris configured to: set a transmit power for a sidelink discovery signal,and transmit the sidelink discovery signal with the transmit power,wherein the transmit power is determined based on discMaxTxPower, andwherein based on the UE being configured with a range class, thediscMaxTxPower informs a parameter used to calculate a maximum transmitpower of the UE configured with the range class.
 7. The UE of claim 6,wherein the range class is any one of short, medium and long.
 8. The UEof claim 6, wherein the discMaxTxPower is separately provided for eachrange class configured for the UE.
 9. The UE of claim 6, wherein theprocessor receives the discMaxTxPower from a base station.
 10. The UE ofclaim 9, wherein the UE transmits the sidelink discovery signal toanother UE in a cell coverage of the base station.